Christopher Ballew 1, Patricia Ramey 2 1 Department of Biology, Central College, 812 E University,...
1
Christopher Ballew 1 , Patricia Ramey 2 1 Department of Biology, Central College, 812 E University, Pella, IA 50219 2 Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ. 08901 Contact Info: Contact Info: [email protected] ; ( 515) 371-4530 515) 371-4530 Polygordius Polygordius sp. nov sp. nov on the Move! on the Move! What this Marine Worm and Other Macrofauna What this Marine Worm and Other Macrofauna Can Tell You About Where to Live and When to Move Can Tell You About Where to Live and When to Move The main goal of this study was to examine The main goal of this study was to examine the habitat preference, capacity and mode of the habitat preference, capacity and mode of post-settlement movement of post-settlement movement of Polygordius Polygordius sp. sp. nov (Ramey 2005). We examined the nov (Ramey 2005). We examined the distribution of distribution of Polygordius Polygordius sp. sp. and other and other macrofaunal taxa (i.e. polychaetes, macrofaunal taxa (i.e. polychaetes, crustaceans, bivalves, nemerteans) in crests crustaceans, bivalves, nemerteans) in crests compared to troughs of sand ripples on the compared to troughs of sand ripples on the inner continental shelf, LEO-15, New Jersey. inner continental shelf, LEO-15, New Jersey. Sediment parameters such as grain size and Sediment parameters such as grain size and organic content were examined to help organic content were examined to help explain observed patterns. In addition, we explain observed patterns. In addition, we experimentally tested whether experimentally tested whether Polygordius Polygordius sp. sp. exhibited post-settlement movement and if exhibited post-settlement movement and if more movement occurred when they found more movement occurred when they found themselves in an unfavorable habitat (e.g. themselves in an unfavorable habitat (e.g. I would like thank my mentors Patricia Ramey and Judy I would like thank my mentors Patricia Ramey and Judy Grassle for their support and encouragement. Special Grassle for their support and encouragement. Special thanks go to Patricia for all her time spent helping with thanks go to Patricia for all her time spent helping with my research project, and befriending me, as well as to my research project, and befriending me, as well as to Drs. Russell Benedict and Paul Weihe for their kind Drs. Russell Benedict and Paul Weihe for their kind letters of recommendation. Finally, I would like to thank letters of recommendation. Finally, I would like to thank the LEO-15 divers who collected my core samples as well the LEO-15 divers who collected my core samples as well as NSF and the RIOS program here at Rutgers for funding as NSF and the RIOS program here at Rutgers for funding INTRODUCTION INTRODUCTION GOALS GOALS QUESTIONS QUESTIONS 1. Is there a difference in abundance 1. Is there a difference in abundance of of Polygordius Polygordius sp. and other macrofaunal sp. and other macrofaunal organisms in the troughs compared to crests organisms in the troughs compared to crests of sand ripples at LEO-15 (12 m depth), and of sand ripples at LEO-15 (12 m depth), and can patterns in abundance be related to can patterns in abundance be related to sediment grain size, and/or organic content sediment grain size, and/or organic content of the sediment? of the sediment? (Examined with field collections from (Examined with field collections from LEO-15) LEO-15) 2. Does 2. Does Polygordius Polygordius sp. exhibit post- sp. exhibit post- settlement movement and if it does which settlement movement and if it does which type is more common: subsurface movement, type is more common: subsurface movement, active bedload or active suspended load? active bedload or active suspended load? (Examined using mini and racetrack (Examined using mini and racetrack flumes) flumes) 3. Is there more post-settlement 3. Is there more post-settlement movement if movement if Polygordius Polygordius sp. is present in sp. is present in favorable ones (organic sediments/with favorable ones (organic sediments/with food)? food)? (Examined (Examined using mini and racetrack using mini and racetrack flumes) flumes) METHODS METHODS Field Collections: Field Collections: Macrofaunal cores were Macrofaunal cores were collected at Station 9 at collected at Station 9 at Rutgers Long-term Ecosystem Rutgers Long-term Ecosystem Observatory, LEO-15 (39˚ 28' Observatory, LEO-15 (39˚ 28' N, 74˚ 15' W). Station 9 is ~ N, 74˚ 15' W). Station 9 is ~ 12 m deep, and is a coarse 12 m deep, and is a coarse sand habitat with ripples 10- sand habitat with ripples 10- 12.5 cm high and 35 cm apart 12.5 cm high and 35 cm apart at the time samples were at the time samples were collected. A total of 16 cores collected. A total of 16 cores were collected by divers were collected by divers consisting of crest/ trough consisting of crest/ trough pair samples each taken ~ 2 m pair samples each taken ~ 2 m apart on May 19, 2005. Five apart on May 19, 2005. Five crest/trough (n total=10) crest/trough (n total=10) samples were used for samples were used for macrofaunal analyses and 3 macrofaunal analyses and 3 others were used for organic others were used for organic carbon analyses of the top 1 carbon analyses of the top 1 cm of sediment. Macrofaunal cm of sediment. Macrofaunal cores were preserved in 4% cores were preserved in 4% formalin and transferred to formalin and transferred to 70% ethanol with Rose Bengal. 70% ethanol with Rose Bengal. Macrofaunal taxa were sorted Macrofaunal taxa were sorted and enumerated. After cores and enumerated. After cores were sorted, grain size was were sorted, grain size was determined using stacked determined using stacked sieves and dry weight sieves and dry weight measures. Organic carbon measures. Organic carbon analysis was preformed using a analysis was preformed using a Carlo Erba elemental analyzer. Carlo Erba elemental analyzer. A Van Veen grab (0.04 m A Van Veen grab (0.04 m 2 )was )was used to collect live used to collect live Polygordius Polygordius sp. for experiments. sp. for experiments. Macrofaunal communities in sandy sediments Macrofaunal communities in sandy sediments on the inner continental shelf off New on the inner continental shelf off New Jersey are often dominated by high densities Jersey are often dominated by high densities of an undescribed polychaete ( of an undescribed polychaete ( Polygordius Polygordius sp. sp. nov), formerly considered to be a member of nov), formerly considered to be a member of the little-studied Archiannelida (Ramey the little-studied Archiannelida (Ramey 2005). These sediments are transported by 2005). These sediments are transported by waves, tidal currents, and storms and this waves, tidal currents, and storms and this study was designed to examine certain study was designed to examine certain aspects of this worm’s habitat preferences, aspects of this worm’s habitat preferences, and how it makes a living in these and how it makes a living in these physically disturbed habitats. Spatial physically disturbed habitats. Spatial patterns (e.g. abundance, distribution, patterns (e.g. abundance, distribution, composition) of macrofauna in soft-sediment composition) of macrofauna in soft-sediment communities are greatly influenced by the communities are greatly influenced by the characteristics of the sediment in which characteristics of the sediment in which they live, such as organic content, grain they live, such as organic content, grain size, dissolved oxygen, stability and size, dissolved oxygen, stability and porosity (Lenihan & Micheli, 2001; porosity (Lenihan & Micheli, 2001; Snelgrove, 2001). Of these, we measured Snelgrove, 2001). Of these, we measured organic content and grain size. Although organic content and grain size. Although looking at where larvae of benthic organisms looking at where larvae of benthic organisms settle is important to gain an understanding settle is important to gain an understanding of faunal patterns, it may be more of faunal patterns, it may be more interesting to ask where they move after interesting to ask where they move after settlement. This question has never been settlement. This question has never been addressed for addressed for Polygordius Polygordius sp. We tested sp. We tested several means of post-settlement movement several means of post-settlement movement using two flumes located at the Institute using two flumes located at the Institute for Marine and Coastal Sciences, Rutgers for Marine and Coastal Sciences, Rutgers University, NJ). In the minifliume we University, NJ). In the minifliume we examined subsurface movement, whereas in the examined subsurface movement, whereas in the racetrack flume, we examined whether racetrack flume, we examined whether Polygordius Polygordius sp. would actively move into the sp. would actively move into the water column and be either transported as water column and be either transported as bedload or as suspended load. There is bedload or as suspended load. There is direct evidence that several organisms direct evidence that several organisms including polychaetes actively enter the including polychaetes actively enter the water column to migrate (e.g. Cummings et. water column to migrate (e.g. Cummings et. al. 1995; Olivier et. al. 1996; Stocks al. 1995; Olivier et. al. 1996; Stocks 2002). We used two sediment treatments 2002). We used two sediment treatments (inorganic and organic) to determine whether (inorganic and organic) to determine whether they would affect the quantity of worm they would affect the quantity of worm movement (e.g. Olivier et al. 1996; Stocks movement (e.g. Olivier et al. 1996; Stocks 2002). 2002). LEO-15 LEO-15 Station 9 Station 9 Field Station Field Station ABSTRACT ABSTRACT Van Veen Grab Van Veen Grab Miniflume: Miniflume: Polygordius Polygordius sp. was starved for ~24 h and acclimated for 30 sp. was starved for ~24 h and acclimated for 30 min (20˚C). A sediment tray was divided into 6 cells, min (20˚C). A sediment tray was divided into 6 cells, arranged in 2 rows of alternating sediment treatments with arranged in 2 rows of alternating sediment treatments with a removable plastic divider and placed in the flume. One a removable plastic divider and placed in the flume. One treatment was fresh organic sediment (Station 9) and the treatment was fresh organic sediment (Station 9) and the other was Station 9 baked (375 °C for 24 h) sediment other was Station 9 baked (375 °C for 24 h) sediment (inorganic). The same number of (inorganic). The same number of Polygordius Polygordius sp. (4-7 sp. (4-7 individuals) was placed in the center of each cell, and individuals) was placed in the center of each cell, and left to burrow (1 min). The flume was filled to a 5 cm left to burrow (1 min). The flume was filled to a 5 cm depth with filtered seawater at ~20 °C and flow was 1.04 depth with filtered seawater at ~20 °C and flow was 1.04 cm cm -1 -1 . After ~ 68-96 . After ~ 68-96 h the divider was h the divider was replaced and the replaced and the number of worms number of worms within each cell within each cell was counted. This was counted. This experiment was also experiment was also performed in still performed in still water conditions. water conditions. Racetrack flume: Racetrack flume: Set up included a down-stream bedload Set up included a down-stream bedload trap to catch trap to catch Polygordius Polygordius sp sp . . transported transported as bedload, and plankton net designed as bedload, and plankton net designed to catch to catch Polygordius Polygordius sp. transported as sp. transported as suspended load. Upstream of this was a suspended load. Upstream of this was a 2 celled sediment tray. Cell 1: 2 celled sediment tray. Cell 1: (organic sediment, 12 (organic sediment, 12 Polygordius Polygordius sp.) and sp.) and Cell 2: (inorganic sediment, 13 Cell 2: (inorganic sediment, 13 Polygordius Polygordius sp.). Water temperature was 22 sp.). Water temperature was 22 °C and velocity 18 cm °C and velocity 18 cm -1 -1 . The exp. was . The exp. was run for ~18 h and the trap/net were run for ~18 h and the trap/net were checked for worms every 2 h for the checked for worms every 2 h for the first 6 h. first 6 h. RESULTS RESULTS ACKNOWLEDGMENTS ACKNOWLEDGMENTS DISCUSSION OF RESULTS DISCUSSION OF RESULTS Mini flume: still Mini flume: still water water 0 2 4 6 1 2 3 4 5 6 Treatm entcells (organic sedim ent) Polygordius sp.(#) B Control Initial Initial Final Final Fig. 8(A) Bar graph showing initial vs final numbers of Polygordius sp. in A. organic vs inorganic sediment treatment cells B. the control (organic treatment cells only) under still water conditions. Fig. 9 Pie charts showing initial and final percentages of Polygordius sp. in organic vs inorganic sediment treatments under still water conditions. Organic Organic Inorgan Inorgan ic ic 0 2 4 6 8 10 12 14 1 2 3 4 5 6 Treatment cells organic inorganic 0 0 0 A Replicate 1 100% 0% Replicate 1 Mini flume: flow Mini flume: flow 0 2 4 6 8 10 12 14 16 1 2 3 4 5 6 Treatm entcells Polygordius sp .(#) Initial Initial Final Final 0 2 4 6 8 10 12 14 1 2 3 4 5 6 Treatm entcells Polygordius sp.(#) 0 0 organic inorganic organic inorganic 48% 52% Fig. 6 Bar graph showing initial vs final numbers of Polygordius sp. in organic vs inorgainic sediment treatment cells under flow conditions A. rep. #1 B. rep. #2 Fig. 7 Pie charts showing initial and final percentages of Polygordius sp. in organic vs inorganic sediment treatments under flow conditions A. rep. #1 B. replicate #2. Note: organic and inorganic treatment cells have been combined. Organic Organic Inorgan Inorgan ic ic B Replicate 2 A. Replicate 1 Mini and racetrack flumes Mini and racetrack flumes 50% 50% 78% 22% 48% 52% B Replicate 2 A Replicate 1 84% 16% Initial Initial Final Final Fig. 1 Bar graph showing density of (A) Polygordius sp. (B) bivalves in ripple crests vs troughs with 95% confidence intervals, n=5. Note: scale on y-axes differ. C ores 1-3,5 0 20 40 60 80 > 2000 1000-2000 500-1000 300-500 >100 G rain S ize C ategories Percent com position Trough Crest C ore 4 0 20 40 60 80 > 2000 1000-2000 500-1000 300-500 >100 G rain S ize C ategories Percent com position (µm) (µm) Fig. 5. Bar graph showing percent total carbon in ripple crests vs troughs. Ripples: Crests vs troughs, LEO-15 Ripples: Crests vs troughs, LEO-15 Fig. 3 Plot showing percent composition of eight grain size categories in ripple crests vs troughs with 95% confidence intervals (n=4). Fig. 4 Plot showing percent composition of eight grain size categories in ripple crests vs troughs of core 4 . . 0 0.1 0.2 0.3 C ore 1 C o re 2 C o re 3 R ipple N um ber % Carbon Content Fig. 2 Bar graph showing density of polychaetes, crustaceans and nemerteans with 95% confidence intervals, n=5. Polygordius sp. 0 100 200 300 400 Density (m -2 ) Bivalves 0 1000 2000 3000 4000 5000 Density (m -2 ) 0 500 1000 1500 2000 2500 Density (m -2 ) Crest Crest Trough Trough Crest Crest Trough Trough Crest Crest Trough Trough Ripple crests vs. troughs, LEO- Ripple crests vs. troughs, LEO- 15: 15: Macrofaunal core samples showed that Macrofaunal core samples showed that Polygordius Polygordius sp. and bivalve densities were sp. and bivalve densities were higher in crests compared to troughs (Fig. higher in crests compared to troughs (Fig. 1 A, B). Other polychaetes, crustaceans, 1 A, B). Other polychaetes, crustaceans, and nemerteans showed the opposite trend and nemerteans showed the opposite trend with higher densities in troughs (Fig. 2). with higher densities in troughs (Fig. 2). These trends may be a result of sediment These trends may be a result of sediment grain size differences observed in crests grain size differences observed in crests vs. troughs. With the exception of core 4, vs. troughs. With the exception of core 4, crests had a higher proportion (60%) of crests had a higher proportion (60%) of coarse sand (500-1000 µm) compared to coarse sand (500-1000 µm) compared to troughs (40%), (Fig. 3). Troughs had a troughs (40%), (Fig. 3). Troughs had a greater proportion (50%) of fine sand (100- greater proportion (50%) of fine sand (100- 500 µm) compared to crests (20% ), (Fig. 500 µm) compared to crests (20% ), (Fig. 3). Core 4 showed the reverse grain size 3). Core 4 showed the reverse grain size and faunal patterns which suggests that the and faunal patterns which suggests that the crest and trough core samples may have been crest and trough core samples may have been switched during sample collection (Fig. 4). switched during sample collection (Fig. 4). With the exception of one core organic With the exception of one core organic carbon content was not different between carbon content was not different between crests and troughs (Fig. 5) and therefore crests and troughs (Fig. 5) and therefore probably did not influence faunal patterns. probably did not influence faunal patterns. High amounts of carbon in core 3 may have High amounts of carbon in core 3 may have been due to a dead macrofaunal organism in been due to a dead macrofaunal organism in the sample. the sample. Miniflume: Miniflume: In the miniflume, under In the miniflume, under still and low flow water conditions, still and low flow water conditions, Polygordius Polygordius sp. exhibited subsurface movement sp. exhibited subsurface movement which was preferentially directed toward which was preferentially directed toward organic sediments (Figs. 6-8A, 9). Pie organic sediments (Figs. 6-8A, 9). Pie charts show that at the beginning of the charts show that at the beginning of the experiments there were ~ 50:50 experiments there were ~ 50:50 Polygordius Polygordius sp. in organic vs. inorganic sediments, sp. in organic vs. inorganic sediments, whereas at the end at least 78% of whereas at the end at least 78% of Polygordius Polygordius sp. were in organic sediment sp. were in organic sediment (Fig. 7, 9). In addition, movement between (Fig. 7, 9). In addition, movement between cells was much greater when cells was much greater when Polygordius Polygordius sp. sp. was present in alternating was present in alternating inorganic/organic sediment treatments inorganic/organic sediment treatments compared to a control containing only compared to a control containing only organic sediment (Fig. 8 A vs B control). organic sediment (Fig. 8 A vs B control). Racetrack flume: Racetrack flume: Very few Very few Polygordius Polygordius sp. moved by means of active bedload or sp. moved by means of active bedload or suspended-load transport (Fig. 10). The few suspended-load transport (Fig. 10). The few individuals that were found in the bedload individuals that were found in the bedload trap moved within the first 2 h of the trap moved within the first 2 h of the experiment and were likely those that may experiment and were likely those that may Inorgan Inorgan ic ic sedimen sedimen t organic organic 232.5 cm 232.5 cm 25 cm 25 cm 1 6 .8 1 6 .8 c m c m 20.8 cm 20.8 cm Plankton Net Treatment tray Bedload trap 21 cm 21 cm 30 cm 30 cm A B B Macrofaunal core samples collected from Macrofaunal core samples collected from ripple crests and troughs at LEO-15, New ripple crests and troughs at LEO-15, New Jersey, revealed that bivalve densities were Jersey, revealed that bivalve densities were higher in crests compared to troughs. The higher in crests compared to troughs. The opposite trend was found for polychaetes, opposite trend was found for polychaetes, crustaceans, and nemerteans with higher crustaceans, and nemerteans with higher densities in ripple troughs. These patterns densities in ripple troughs. These patterns may be a result of sediment grain size may be a result of sediment grain size differences observed between crests and differences observed between crests and troughs with crests having a higher troughs with crests having a higher proportion (60%) of coarse sand (500-1000 proportion (60%) of coarse sand (500-1000 µm) compared to troughs (40%) . Percent µm) compared to troughs (40%) . Percent total organic carbon did not differ between total organic carbon did not differ between crests and troughs. crests and troughs. Polygordius Polygordius sp. exhibited sp. exhibited subsurface post-settlement movement under subsurface post-settlement movement under still water and low flow conditions that was still water and low flow conditions that was preferentially directed toward organic preferentially directed toward organic sediments. Very few sediments. Very few Polygordius Polygordius sp. moved sp. moved by means of active bedload or suspended-load by means of active bedload or suspended-load transport. transport. 0 2 4 6 8 10 12 14 Treatm entC ells P olygordiu p . ( Initial Initial Final Final organic inorganic Fig. 10 Bar graph showing initial vs. final numbers of Polygordius sp. in organic vs. inorganic treatments. Racetrack flume: Racetrack flume:
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Transcript of Christopher Ballew 1, Patricia Ramey 2 1 Department of Biology, Central College, 812 E University,...
Christopher Ballew1, Patricia Ramey2
1Department of Biology, Central College, 812 E University, Pella, IA 502192Institute of Marine and Coastal Sciences, Rutgers University, 71 Dudley Road, New Brunswick, NJ. 08901
Contact Info: Contact Info: [email protected]; (515) 371-4530515) 371-4530
PolygordiusPolygordius sp. nov sp. nov on the Move!on the Move! What this Marine Worm and Other What this Marine Worm and Other Macrofauna Can Tell You About Where to Live and When to MoveMacrofauna Can Tell You About Where to Live and When to Move
The main goal of this study was to examine the habitat The main goal of this study was to examine the habitat preference, capacity and mode of post-settlement movement preference, capacity and mode of post-settlement movement of of Polygordius Polygordius sp. nov (Ramey 2005). We examined the sp. nov (Ramey 2005). We examined the distribution of distribution of Polygordius Polygordius sp.sp. and other macrofaunal taxa and other macrofaunal taxa (i.e. polychaetes, crustaceans, bivalves, nemerteans) in crests (i.e. polychaetes, crustaceans, bivalves, nemerteans) in crests compared to troughs of sand ripples on the inner continental compared to troughs of sand ripples on the inner continental shelf, LEO-15, New Jersey. Sediment parameters such as shelf, LEO-15, New Jersey. Sediment parameters such as grain size and organic content were examined to help explain grain size and organic content were examined to help explain observed patterns. In addition, we experimentally tested observed patterns. In addition, we experimentally tested whether whether PolygordiusPolygordius sp. exhibited post-settlement movement sp. exhibited post-settlement movement and if more movement occurred when they found themselves and if more movement occurred when they found themselves in an unfavorable habitat (e.g. inorganic sediments/no food). in an unfavorable habitat (e.g. inorganic sediments/no food). Three modes of movement were examined: subsurface Three modes of movement were examined: subsurface movement within the sediment, active bedload transport, and movement within the sediment, active bedload transport, and active water column transport.active water column transport.
I would like thank my mentors Patricia Ramey and Judy Grassle for their I would like thank my mentors Patricia Ramey and Judy Grassle for their support and encouragement. Special thanks go to Patricia for all her time spent support and encouragement. Special thanks go to Patricia for all her time spent helping with my research project, and befriending me, as well as to Drs. Russell helping with my research project, and befriending me, as well as to Drs. Russell Benedict and Paul Weihe for their kind letters of recommendation. Finally, I Benedict and Paul Weihe for their kind letters of recommendation. Finally, I would like to thank the LEO-15 divers who collected my core samples as well as would like to thank the LEO-15 divers who collected my core samples as well as NSF and the RIOS program here at Rutgers for funding my internship.NSF and the RIOS program here at Rutgers for funding my internship.
INTRODUCTIONINTRODUCTION
GOALSGOALS
QUESTIONS QUESTIONS
1. Is there a difference in abundance of 1. Is there a difference in abundance of Polygordius Polygordius sp. sp. and other macrofaunal organisms in the troughs compared and other macrofaunal organisms in the troughs compared to crests of sand ripples at LEO-15 (12 m depth), and can to crests of sand ripples at LEO-15 (12 m depth), and can patterns in abundance be related to sediment grain size, patterns in abundance be related to sediment grain size, and/or organic content of the sediment? and/or organic content of the sediment?
(Examined with field collections from LEO-15)(Examined with field collections from LEO-15)
2. Does 2. Does Polygordius Polygordius sp. exhibit post-settlement movement sp. exhibit post-settlement movement and if it does which type is more common: subsurface and if it does which type is more common: subsurface movement, active bedload or active suspended load? movement, active bedload or active suspended load?
(Examined using mini and racetrack flumes)(Examined using mini and racetrack flumes)
3. Is there more post-settlement movement if 3. Is there more post-settlement movement if Polygordius Polygordius sp. is present in unfavorable environments (e.g. inorganic sp. is present in unfavorable environments (e.g. inorganic sediments/no food) than if they are in favorable ones sediments/no food) than if they are in favorable ones (organic sediments/with food)?(organic sediments/with food)?
(Examined(Examined using mini and racetrack flumes) using mini and racetrack flumes)
METHODSMETHODSField Collections:Field Collections:Macrofaunal cores were collected at Macrofaunal cores were collected at Station 9 at Rutgers Long-term Ecosystem Station 9 at Rutgers Long-term Ecosystem Observatory, LEO-15 (39˚ 28' N, 74˚ 15' Observatory, LEO-15 (39˚ 28' N, 74˚ 15' W). Station 9 is ~ 12 m deep, and is a W). Station 9 is ~ 12 m deep, and is a coarse sand habitat with ripples 10-12.5 coarse sand habitat with ripples 10-12.5 cm high and 35 cm apart at the time cm high and 35 cm apart at the time samples were collected. A total of 16 cores samples were collected. A total of 16 cores were collected by divers consisting of were collected by divers consisting of crest/ trough pair samples each taken ~ 2 crest/ trough pair samples each taken ~ 2 m apart on May 19, 2005. Five m apart on May 19, 2005. Five crest/trough (n total=10) samples were crest/trough (n total=10) samples were used for macrofaunal analyses and 3 used for macrofaunal analyses and 3 others were used for organic carbon others were used for organic carbon analyses of the top 1 cm of sediment. analyses of the top 1 cm of sediment. Macrofaunal cores were preserved in 4% Macrofaunal cores were preserved in 4% formalin and transferred to 70% ethanol formalin and transferred to 70% ethanol with Rose Bengal. Macrofaunal taxa were with Rose Bengal. Macrofaunal taxa were sorted and enumerated. After cores were sorted and enumerated. After cores were sorted, grain size was determined using sorted, grain size was determined using stacked sieves and dry weight measures. stacked sieves and dry weight measures. Organic carbon analysis was preformed Organic carbon analysis was preformed using a Carlo Erba elemental analyzer. A using a Carlo Erba elemental analyzer. A Van Veen grab (0.04 mVan Veen grab (0.04 m22)was used to )was used to collect live collect live Polygordius Polygordius sp. for sp. for experiments. experiments.
Macrofaunal communities in sandy sediments on the inner Macrofaunal communities in sandy sediments on the inner continental shelf off New Jersey are often dominated by high continental shelf off New Jersey are often dominated by high densities of an undescribed polychaete (densities of an undescribed polychaete (PolygordiusPolygordius sp. nov), sp. nov), formerly considered to be a member of the little-studied formerly considered to be a member of the little-studied Archiannelida (Ramey 2005). These sediments are Archiannelida (Ramey 2005). These sediments are transported by waves, tidal currents, and storms and this transported by waves, tidal currents, and storms and this study was designed to examine certain aspects of this worm’s study was designed to examine certain aspects of this worm’s habitat preferences, and how it makes a living in these habitat preferences, and how it makes a living in these physically disturbed habitats. Spatial patterns (e.g. physically disturbed habitats. Spatial patterns (e.g. abundance, distribution, composition) of macrofauna in soft-abundance, distribution, composition) of macrofauna in soft-sediment communities are greatly influenced by the sediment communities are greatly influenced by the characteristics of the sediment in which they live, such as characteristics of the sediment in which they live, such as organic content, grain size, dissolved oxygen, stability and organic content, grain size, dissolved oxygen, stability and porosity (Lenihan & Micheli, 2001; Snelgrove, 2001). Of porosity (Lenihan & Micheli, 2001; Snelgrove, 2001). Of these, we measured organic content and grain size. Although these, we measured organic content and grain size. Although looking at where larvae of benthic organisms settle is looking at where larvae of benthic organisms settle is important to gain an understanding of faunal patterns, it may important to gain an understanding of faunal patterns, it may be more interesting to ask where they move after settlement. be more interesting to ask where they move after settlement. This question has never been addressed for This question has never been addressed for Polygordius Polygordius sp. sp. We tested several means of post-settlement movement using We tested several means of post-settlement movement using two flumes located at the Institute for Marine and Coastal two flumes located at the Institute for Marine and Coastal Sciences, Rutgers University, NJ). In the minifliume we Sciences, Rutgers University, NJ). In the minifliume we examined subsurface movement, whereas in the racetrack examined subsurface movement, whereas in the racetrack flume, we examined whether flume, we examined whether PolygordiusPolygordius sp. would actively sp. would actively move into the water column and be either transported as move into the water column and be either transported as bedload or as suspended load. There is direct evidence that bedload or as suspended load. There is direct evidence that several organisms including polychaetes actively enter the several organisms including polychaetes actively enter the water column to migrate (e.g. Cummings et. al. 1995; Olivier water column to migrate (e.g. Cummings et. al. 1995; Olivier et. al. 1996; Stocks 2002). We used two sediment treatments et. al. 1996; Stocks 2002). We used two sediment treatments (inorganic and organic) to determine whether they would (inorganic and organic) to determine whether they would affect the quantity of worm movement (e.g. Olivier et al. 1996; affect the quantity of worm movement (e.g. Olivier et al. 1996; Stocks 2002).Stocks 2002).
LEO-15LEO-15
Station 9Station 9
Field StationField Station
ABSTRACTABSTRACT
Van Veen GrabVan Veen Grab
Miniflume: Miniflume: Polygordius Polygordius sp. was starved for ~24 h and acclimated for 30 min (20˚C). A sediment sp. was starved for ~24 h and acclimated for 30 min (20˚C). A sediment tray was divided into 6 cells, arranged in 2 rows of alternating sediment treatments tray was divided into 6 cells, arranged in 2 rows of alternating sediment treatments with a removable plastic divider and placed in the flume. One treatment was fresh with a removable plastic divider and placed in the flume. One treatment was fresh organic sediment (Station 9) and the other was Station 9 baked (375 °C for 24 h) organic sediment (Station 9) and the other was Station 9 baked (375 °C for 24 h) sediment (inorganic). The same number of sediment (inorganic). The same number of Polygordius Polygordius sp. (4-7 individuals) was sp. (4-7 individuals) was placed in the center of each cell, and left to burrow (1 min). The flume was filled to placed in the center of each cell, and left to burrow (1 min). The flume was filled to a 5 cm depth with filtered seawater at ~20 °C and flow was 1.04 cma 5 cm depth with filtered seawater at ~20 °C and flow was 1.04 cm-1-1. After ~ 68-96 . After ~ 68-96 h the divider was replaced h the divider was replaced
and the number of worms and the number of worms within each cell was within each cell was counted. This experiment counted. This experiment was also performed in still was also performed in still water conditions.water conditions.
Racetrack flume: Racetrack flume: Set up included a down-stream bedload trap to catch Set up included a down-stream bedload trap to catch Polygordius Polygordius spsp. . transported as bedload, and plankton transported as bedload, and plankton net designed to catch net designed to catch Polygordius Polygordius sp. transported as sp. transported as suspended load. Upstream of this was a 2 celled suspended load. Upstream of this was a 2 celled sediment tray. Cell 1: (organic sediment, 12 sediment tray. Cell 1: (organic sediment, 12 Polygordius Polygordius sp.) and Cell 2: (inorganic sediment, 13 sp.) and Cell 2: (inorganic sediment, 13 Polygordius Polygordius sp.). Water temperature was 22 °C and velocity 18 cmsp.). Water temperature was 22 °C and velocity 18 cm-1-1. . The exp. was run for ~18 h and the trap/net were The exp. was run for ~18 h and the trap/net were checked for worms every 2 h for the first 6 h.checked for worms every 2 h for the first 6 h.
RESULTSRESULTS
ACKNOWLEDGMENTSACKNOWLEDGMENTS
DISCUSSION OF RESULTSDISCUSSION OF RESULTS
Mini flume: still waterMini flume: still water
0
2
4
6
1 2 3 4 5 6
Treatment cells (organic sediment)
Po
lyg
ord
ius
sp
. (#
)
B Control
InitialInitial FinalFinal
Fig. 8(A) Bar graph showing initial vs final numbers of Polygordius sp. in A. organic vs inorganic sediment treatment cells B. the control (organic treatment cells only) under still water conditions.
Fig. 9 Pie charts showing initial and final percentages of Polygordius sp. in organic vs inorganic sediment treatments under still water conditions.
OrganicOrganicInorganicInorganic
02468
101214
1 2 3 4 5 6
Treatment cells
organic inorganic
0 00
A Replicate 1
100%
0%Replicate 1
Mini flume: flowMini flume: flow
02468
10121416
1 2 3 4 5 6
Treatment cellsP
oly
go
rdiu
s sp
.(#
)
InitialInitial FinalFinal
02468
101214
1 2 3 4 5 6
Treatment cells
Po
lyg
ord
ius
sp
.(#)
0
0
organic inorganic
organic inorganic
48%52%
Fig. 6 Bar graph showing initial vs final numbers of Polygordius sp. in organic vs inorgainic sediment treatment cells under flow conditions A. rep. #1 B. rep. #2
Fig. 7 Pie charts showing initial and final percentages of Polygordius sp. in organic vs inorganic sediment treatments under flow conditions A. rep. #1 B. replicate #2. Note: organic and inorganic treatment cells have been combined.
OrganicOrganicInorganicInorganic
B Replicate 2
A. Replicate 1
Mini and racetrack flumesMini and racetrack flumes
50%50%
78%
22%
48%52%
B Replicate 2
A Replicate 1
84%
16%InitialInitial FinalFinal
Fig. 1 Bar graph showing density of (A) Polygordius sp. (B) bivalves in ripple crests vs troughs with 95% confidence intervals, n=5. Note: scale on y-axes differ.
Cores 1-3, 5
020406080
> 2000 1000-2000 500-1000 300-500 >100
Grain Size Categories
Perc
ent
com
posi
tion
Trough
Crest
Core 4
020406080
> 2000 1000-2000 500-1000 300-500 >100
Grain Size Categories
Per
cen
t co
mp
osi
tio
n
(µm)
(µm)
Fig. 5. Bar graph showing percent total carbon in ripple crests vs troughs.
Ripples: Crests vs troughs, LEO-15 Ripples: Crests vs troughs, LEO-15
Fig. 3 Plot showing percent composition of eight grain size categories in ripple crests vs troughs with 95% confidence intervals (n=4).
Fig. 4 Plot showing percent composition of eight grain size categories in ripple crests vs
troughs of core 4..
0
0.1
0.2
0.3
Core 1 Core 2 Core 3
Ripple Number
% C
arbo
n C
onte
nt
Fig. 2 Bar graph showing density of polychaetes, crustaceans and nemerteans with 95% confidence intervals, n=5.
Polygordius sp.
0
100
200
300
400
Den
sity
(m-2
)
Bivalves
0
1000
2000
3000
4000
5000
Den
sity
(m
-2)
0500
1000150020002500
Den
sity
(m-2
)
CrestCrest TroughTrough CrestCrest TroughTrough
CrestCrest TroughTrough
Ripple crests vs. troughs, LEO-15:Ripple crests vs. troughs, LEO-15: Macrofaunal Macrofaunal core samples showed that core samples showed that Polygordius Polygordius sp. and bivalve sp. and bivalve densities were higher in crests compared to troughs (Fig. 1 densities were higher in crests compared to troughs (Fig. 1 A, B). Other polychaetes, crustaceans, and nemerteans A, B). Other polychaetes, crustaceans, and nemerteans showed the opposite trend with higher densities in troughs showed the opposite trend with higher densities in troughs (Fig. 2). These trends may be a result of sediment grain size (Fig. 2). These trends may be a result of sediment grain size differences observed in crests vs. troughs. With the differences observed in crests vs. troughs. With the exception of core 4, crests had a higher proportion (60%) of exception of core 4, crests had a higher proportion (60%) of coarse sand (500-1000 µm) compared to troughs (40%), coarse sand (500-1000 µm) compared to troughs (40%), (Fig. 3). Troughs had a greater proportion (50%) of fine (Fig. 3). Troughs had a greater proportion (50%) of fine sand (100-500 µm) compared to crests (20% ), (Fig. 3). Core sand (100-500 µm) compared to crests (20% ), (Fig. 3). Core 4 showed the reverse grain size and faunal patterns which 4 showed the reverse grain size and faunal patterns which suggests that the crest and trough core samples may have suggests that the crest and trough core samples may have been switched during sample collection (Fig. 4). With the been switched during sample collection (Fig. 4). With the exception of one core organic carbon content was not exception of one core organic carbon content was not different between crests and troughs (Fig. 5) and therefore different between crests and troughs (Fig. 5) and therefore probably did not influence faunal patterns. High amounts of probably did not influence faunal patterns. High amounts of carbon in core 3 may have been due to a dead macrofaunal carbon in core 3 may have been due to a dead macrofaunal organism in the sample. organism in the sample.
Miniflume:Miniflume: In the miniflume, under still and low flow In the miniflume, under still and low flow water conditions, water conditions, Polygordius Polygordius sp. exhibited subsurface sp. exhibited subsurface movement which was preferentially directed toward organic movement which was preferentially directed toward organic sediments (Figs. 6-8A, 9). Pie charts show that at the sediments (Figs. 6-8A, 9). Pie charts show that at the beginning of the experiments there were ~ 50:50 beginning of the experiments there were ~ 50:50 PolygordiusPolygordius sp. in organic vs. inorganic sediments, whereas at the end at sp. in organic vs. inorganic sediments, whereas at the end at least 78% of least 78% of Polygordius Polygordius sp. were in organic sediment (Fig. sp. were in organic sediment (Fig. 7, 9). In addition, movement between cells was much greater 7, 9). In addition, movement between cells was much greater when when Polygordius Polygordius sp. was present in alternating sp. was present in alternating inorganic/organic sediment treatments compared to a inorganic/organic sediment treatments compared to a control containing only organic sediment (Fig. 8 A vs B control containing only organic sediment (Fig. 8 A vs B control). control).
Racetrack flume:Racetrack flume: Very few Very few Polygordius Polygordius sp. moved by sp. moved by means of active bedload or suspended-load transport (Fig. means of active bedload or suspended-load transport (Fig. 10). The few individuals that were found in the bedload trap 10). The few individuals that were found in the bedload trap moved within the first 2 h of the experiment and were likely moved within the first 2 h of the experiment and were likely those that may not have completely burrowed into the those that may not have completely burrowed into the sediment and were swept away when the flow began.sediment and were swept away when the flow began.
InorganicInorganicsedimentsediment
organicorganic
232.5 cm232.5 cm
25 cm25 cm
16.8 cm16.8 cm
20.8 cm20.8 cm
Plankton Net
Treatment tray
Bedload trap
21 cm21 cm
30 cm30 cm
AA
BB
Macrofaunal core samples collected from ripple crests and Macrofaunal core samples collected from ripple crests and troughs at LEO-15, New Jersey, revealed that bivalve troughs at LEO-15, New Jersey, revealed that bivalve densities were higher in crests compared to troughs. The densities were higher in crests compared to troughs. The opposite trend was found for polychaetes, crustaceans, and opposite trend was found for polychaetes, crustaceans, and nemerteans with higher densities in ripple troughs. These nemerteans with higher densities in ripple troughs. These patterns may be a result of sediment grain size differences patterns may be a result of sediment grain size differences observed between crests and troughs with crests having a observed between crests and troughs with crests having a higher proportion (60%) of coarse sand (500-1000 µm) higher proportion (60%) of coarse sand (500-1000 µm) compared to troughs (40%) . Percent total organic carbon compared to troughs (40%) . Percent total organic carbon did not differ between crests and troughs. did not differ between crests and troughs. Polygordius Polygordius sp. sp. exhibited subsurface post-settlement movement under still exhibited subsurface post-settlement movement under still water and low flow conditions that was preferentially water and low flow conditions that was preferentially directed toward organic sediments. Very few directed toward organic sediments. Very few PolygordiusPolygordius sp. sp. moved by means of active bedload or suspended-load moved by means of active bedload or suspended-load transport.transport.
0
2
4
6
8
10
12
14
Treatment Cells
Po
lyg
ord
ius
sp
. (#
)
InitialInitial FinalFinal
organic inorganic
Fig. 10 Bar graph showing initial vs. final numbers of Polygordius sp. in organic vs. inorganic treatments.
Racetrack flume:Racetrack flume:
