What are the Main Types of Coastal Ecosystems?

– Estuaries and Coastal Wetlands• Estuaries are isolated from the open sea, diluted by rivers (brackish water)

– Typically with low diversity but high productivity (abundance of certain species)– Organisms adapted for changing salinities (osmoregulators, osmoconformers)

• Ecosystems include mudflats, seagrass meadows, salt marshes, oyster reefs, and mangroves

– Rocky Intertidal Zones• Zonation based on exposure/desiccation, predation, and competition

– Splash Zone: small barnacles, periwinkles, rock lice; never submerged– High-tide Zone: larger barnacles; tide pools (instant physical changes when tide rises,

exposed for long periods on lowest tides of year)– Mid-tide Zone: mussels, gooseneck barnacles, snails and hermit crabs– Low-tide Zone: sea stars and urchins, red coralline algae, kelps, sea anemones

• Organisms adapted for high wave stress (spines, cement, suction, and burrowing) and fluctuating salinities (re. rain and evaporation)

– Mudflats and Beaches• Mudflats with fine grain sizes (low wave action) more detritus, less oxygen

content; cohesion allows burrowing (ex. worms, clams); probing birds• Wave-exposed beaches with larger grains less detritus and burrowing (low

species diversity: sand crabs, razor clams common)

Figures 13-5 and 13-10

Figures 14-12 and 14-13

Figure 14-21b and 14-22

Figures 14-23 and 14-24

Where are the World’s Coral Reefs?

– Origin and Types of Coral Reefs• Built by Scleractinian Corals: contain zooxanthellae dino-

flagellates; increased metabolism allows deposition of calcium carbonate calyx around polyp (rocky skeletons)

• Evolution of Coral Atolls (ex. Rangiroa, Bikini): fringing reef forms around sinking island barrier reef with channel atoll with lagoon (island consists of coral rock and sand)

• Table Reefs: found in shallow areas of open ocean

– Physical Factors Limiting Reef Growth• Zooxanthellae need clear, warm water no deeper than 60

meters and no colder than 20◦C; bleaching if too warm (zooxanthellae expelled from polyps)

• Sedimentation smothers corals; not found near river mouths• Most common around eastern side of continents; center of coral

biodiversity in Indo-Pacific (ex. 700 coral species in Philippines/Indonesia vs. 60 species in Caribbean)

Figure 5-33

Figures 13-24 to 13-27

Figure 14-27

What are the Main Threats to the World’s Coral Reefs?

– The Nemesis Effect: synergistic effects of multiple stressors (the case for most coral reefs)

• Global Warming: bleaching occurs if water too warm; some reefs expected to benefit (ex. Hawaii)

• Stratospheric Ozone Depletion: increased UV light stresses corals and can lead to bleaching

• Overfishing: including use of dynamite and cyanide; focused efforts on sharks, Napoleon wrasse and bumphead parrotfish, (“brain fishes”) and seahorses

• Diseases: viral and bacterial diseases noted and rising • Eutrophication: increased nitrogen favors growth of

competitive macroalgae (can overgrow corals)• Sedimentation: smothers corals, reducing light and

oxygen uptake; occurs where sewage untreated

Figure 5-35

What are the Most Important Links in the Ocean’s Biogeochemical Cycles?

– The Carbon Cycle• Photosynthesis converts atmospheric carbon dioxide to sugars, which are

consumed by animals• Respiration by animals and plants plus decomposition by bacteria returns

CO2 to atmosphere• Combustion (of fossil fuels) and deforestation increases atmospheric CO2

• CO2 diffuses into ocean, organisms incorporate CaCO3 into bones, shells

– The Nitrogen Cycle• Nitrates and nitrites absorbed by phytoplankton and algae, which are

consumed by animals (nitrogen incorporated into amino acids)• Decomposition returns nitrogenous compounds to water column• Runoff from land masses and eutrophication increase nitrogen levels• Coastal upwelling of deep, nutrient-rich layers increases nitrogen levels

– The Phosphorus Cycle and Silicon• Short-term Cycle: essentially same as nitrogen cycle; phosphorus

incorporated into DNA, ATP; silicon into tests of diatoms• Long-term Cycle: includes incorporation in rocks by sedimentation and

compaction; uplift, exposure, and erosion of rocks returns phosphorus to the water column (over millions of years)

Figure 6-30

Figures 6-31 and 6-32

Figure 14-11