Common aquatic proxies diatoms chrysophytes sponges radiolaria foraminifera* ostracodes Silicates...
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Transcript of Common aquatic proxies diatoms chrysophytes sponges radiolaria foraminifera* ostracodes Silicates...
Common aquatic proxies
diatomschrysophytesspongesradiolariaforaminifera*ostracodes
Silicates
Carbonates
Structural material Group
*agglutinated forams have clastic, not carbonate tests
Diatoms
photo: Yuki Sawai
Unicellular, eukaryotic, generally photosynthetic microorganisms encased in a cell wall impregnated with silica. They tolerate a wide range of thermal, pH and salinity conditions in aquatic habitats and wetland soils.
Centric and pennate diatoms
1. Valve face2. Mantle3. Girdle
(bands = cingula)
1
1
2
2
3
2
3
Diatoms(major groups based on cell
morphology and ornamentation)Eucentric - circular valve outline; radially symmetrical valve
ornamentation.Eccentric - bipolar or multipolar outline; radial symmetry.Araphid - bilateral symmetry to a central thickening (sternum).Monoraphid - bilateral symmetry ; sternum has fissure (raphe)
on onevalve only.
Naviculoid - bilateral symmetry; sternum has raphe on both valves.
Cymbelloid - raphes on both valves; assymetric on either the longitudinal or transverse axis.
Nitzschoid - raphes on both valves raised above valve on keel.Surirelloid - raphes on both valves raised above valve on wing.Epithemoid - raphes on both valves within a canal.
Eucentric diatoms
colony in girdle view
valve view
Thalassiosira Aulacoseira lacustris
Araphid (e.g. “Fragilaria”)
and monoraphid diatoms
(e.g. Cocconeis)
Epivalve (with raphe) Hypovalve ( no raphe)
Naviculoid diatomsPinnularia abaujensis
Diploneis finnica Frustulia rhomboides
Cymbelloid diatoms
Cymbella affinis
Eunotioid diatomsEunotia formica
Nitschzoid diatomskeel
Epithemoid diatoms
canal
Surirelloid diatoms
www.marbot.gu.se/files/melissa/checklist/diatoms.html#list
Diatoms: taxonomic problems(e.g. freshwater and brackish
Fragilariaceae)
AsterionellaCentronellaCeratoneisDiatomaHanneaMeridion
AsterionellaCentronellaCeratoneisDiatomaFragilariaMeridionOpephoraSynedraTetracyclusTabellaria
Krammer & Lange-Bertalot(1991)
Round, Crawford & Mann (1990)
FragilariaFragilariformaPseudostaurosiraPunctastriataStaurosiraStaurosirellaOpephora(*marine)MartyanaCtenophoraNeosynedraSynedraTabulariaTabellariaceae
“Fragilaria”
morphology
Image in light microscope
SEM imagesa) Fragilariformab) Staurosirellac) Punctastriatad) Staurosirae) Pseudostaurosira
a
d
c
e
b
From: Round et al. (1990) The Diatoms. Cambridge U.P.
Diatoms: taxonomic problems - synonymies
In Great Lakes catalogue (www.umich.edu/~phytolab/Great lakes/DiatomHomePage) as Oestrupia zachariasi
In California Academy of Sciences catalogue (www.calacademy.org/research/diatoms)as Oestrupia bicontracta
Examples of applications of diatoms in palaeoenvironmental studies
Sea-level change:western Scotland
Palaeoseismology:Discovery Bay, WA
Palaeolimnology:depth: Lake Oloiden, Kenya
pH: Baby Lake, Ontariotemperature: Längsee, Austria
Diatom record
of sea-levelchange
in an isolationbasin on thewest coast of
Scotland
DiscoveryBay, WA
Diatom record of tsunami
inundation of marshes
Lake Oloiden, Kenya
(planktonic centric)
(salt-tolerant benthic, naviculoid)
Diatom-inferred pH change, Baby Lake, Ontario (1870-1990)
from: Dixit et al. (1992) Water , Air and Soil Pollution, 62, 75-87.
pH
5 6 7
Late-Glacial summer surface water temperature, Längsee (548 m asl),
AustriaPollen Diatoms Surface Water Temp
from: Schmidt et al. (1998) Aquatic Sciences, 60, 56-88.
Chrysophytes
Chrysophyte stomatocyst(resting spore)
Although it is difficult to distinguish species in LM, the resting spores of Chrysophytes may prove useful as supplementary sources of environmental information in freshwater habitats.
Freshwater sponges
(e.g. Heteromyenia sp.?)1. sponge spicules and diatoms (Stump Lake, BC)2. gemmosclere3. mega and microscleres1
2 3
Sponge palaeofaunas, 20 ka BP - PD
(Jackson Pond, KY)
* H. latitientia now restricted to northern New England
*
Radiolarians
Lamprocyclasmaritalis
Lophospyrispentagona
Rhizoplegmaborealia
• marine unicellular protists;• siliceous skeletons in soft
cytoplasm; lipid globules in cytoplasm (and spines?) enhance buoyancy;
•planktonic: occur from surface to depths of several hundred meters;
• size range = 2 - 30 mm diameter;
• families distinguished by skeletal shapes; some groups are solitary, others colonial;
• species abundance related to water temp., salinity, and nutrient status.
source: www. radiolaria.org
An example of the application of radiolarians in
palaeo-oceanographic
studies
from: Pisias et al (2001) Quat. Sci Rev., 20, 1561-1576
Core 1019
Radiolarian assemblages in the Pacific Ocean
Max. factor loadings
from: Pisias et al.(2001) Quat. SciRev., 20, 1561-1576.
Radiolarian assemblages in core 1019 (989 m water depth)
green line = GISP2 18O record; black line=radiolarian record
T1YD
ForaminiferaForaminifera are single-celled protists that live in all marine environments. They inhabit the sea floor (benthonic forms) or the surface layer of the oceans (planktonic forms). Most of the soft tissue of the cell of a foraminifer is enclosed within a test which may be composed of secreted organic compounds and mineral grains cemented together (agglutinated test), or secreted calcite or aragonite (calcareous test). The calcareous tests are divided, in part, into hyaline and porcellaneous types based on the orientation of the calcium carbonate crystallites comprising the test.
Examples of (1) agglutinated and (2) calcareous foraminifers
(2) Elphidium excavatum(1) Textularia forquata
length = 0.18 mm; breadth = 0.09 mm max. diam. = 0.48 mm; thickness = 0.20 mm
foram photos and info. from http://www.cs.uwindsor.ca/meta-index/fossils/woop.html
Examples of applications of foraminifera in
palaeoenvironmental studies: coiling
and ocean temperature
“N. pachy left”
Forams: “aplanktic” episodes in the Red Sea confirm eustatic
lowstands
Low RSL = hypersaline Red Sea = no planktonic forams
from
: R
ohlin
g e
t al. (
1998)
Natu
re,
394,
162-1
65.
Palaeo-temperature, core DSDP-609(N. Atlantic) based on “%N. pachy
left”
100%
0%
Ostracodes
Ostracodes are crustaceans with two calcareous valves hinged along the dorsal margin to form a carapace which is commonly ovate or kidney-shaped. They have adapted to marine environments — oceans, estuaries and lagoons; hypersaline environments; freshwater environments — lakes, ponds, rivers and springs; and terrestrial environments such as the moist humus of forests. The majority of ostracodes are benthonic in habit.
length = 0.69 mmheight = 0.38 mm width = 0.35 mm
source: www.cs.uwindsor.ca/meta-index/fossils/woop.html
Bensonocythere americana
dorsal view
lateral view
Applications of ostracodes in Quaternary palaeoenvironmental research:
Lake Manitoba during the Holocene
from
: C
urr
y (
19
97
) C
an. J. E
art
h S
ci., 3
4, 6
99
-70
8.
1 2 3 4
Salinity(g/L)
Applications of ostracodes:
changes in depth ranges (controlled by water temperature)
record oceanographicconditions on Bahama
Bank
Krithe sp.
pores
4°cooler
2°cooler
from: Rodriguez-Lazaro & Cronin (1999) Palaeo3, 152, 339-364.
Aquatic proxies as sources of proxy data:advantages
• short generation times; quick response to environmental change
• many groups cosmopolitan (cf. regional floras and megafaunas)
• in situ, not derived from surrounding terrestrial habitats, therefore representative of conditions within the water body, rather than the watershed.
Aquatic proxies as sources of proxy data:limitations
•no ‘parent’ for reference material (cf. pollen & spores)
•species concept often difficult to apply;•small forms hard to distinguish in LM;•unstable taxonomies; many synonyms;•meagre ecological information;•often responsive to a wide variety of inter-linked environmental stimuli (water temperature, conductivity, pH, nutrient status, depth);
•small size leads to homogenization by currents, etc. (i.e. allochthonous components common in fossil assemblages).