Lect10 Marine Ecosystems. Estuaries Marine Shores Shallow Marine Waters Oceans Lect07 Marine Ecosystems.

Lect10Marine Ecosystems

• Estuaries

• Marine Shores

• Shallow Marine Waters

• Oceans

Lect07Marine Ecosystems

Estuaries

• An estuary is a transition area between river and sea

• Barrier to flooding• Filter for terrestrial pollutants• Usually found where rivers meet the sea

• Salinity varies with the rise and fall of the tides

• Estuaries are nutrient rich and highly productive

– Primary production: salt marsh grasses, algae

• An abundant supply of food attracts marine invertebrates and fish

– Worms, oysters, crabs – etc – support water fowl, fish

– Important as nurseries of many fish spp.

Salt Marshes and Mangrove Forests

Characteristic Regions of Estuarine Habitat• Important factors:

– Sediment size– Exposure during tidal flux

• Aquatic Bed– Eelgrass – supports epiphytes, prevents

erosion, traps sediment

• Tidal Flats– Store heat, varied salinity, oxygen issues

• Low and Middle Marsh/salt march – pickle weed, cord grass, mangrove

Issues in Estuaries

• Excessive nutrients from adjacent terrestrial areas eutrophication anoxia

• Silt accumulation

• Invasive species

• Impacts of development

• Elkhorn Slough– One of a limited number of estuaries along CA

coast– Relatively well preserved, still – many issues

• Changes in Elkhorn Slough

• Diversion of Salinas River

• Increased tidal flow– Sediment loss

• Construction of railway embankment

• Loss in salt marsh habitat (50% since 1931)– Soil compaction and subsidence– Channel widening

• Coral reefs: formed from the calcium carbonate skeletons of corals (phylum Cnidaria)

• require a solid substrate for attachment

• mutualistic relationship with algae provides corals with organic molecules

• Highly diverse community

Fig. 52-18i

A coral reef in the Red Sea

Intertidal Zones

• An intertidal zone is periodically submerged and exposed by the tides

• variations in temperature and salinity

• the mechanical forces of wave action

• structural adaptations that enable attachment hard substrate

Fig. 52-18g

Rocky intertidal zone on the Oregon coast

Oceans - Geography• Cover 70% of earth’s surface

• Average Depth– Pacific - 4,000 m– Atlantic - 3,900 m– Indian - 3,900 m

• Undersea Trenches– Marianas - 10,000 m deep

• Would engulf Mt. Everest with 2 km to spare.

• Marine Systems – Regions• Littoral: intertidal• Benthic: refers to sea bottom• Neritic: ocean over continental shelf - ~ 100-200m• Oceanic: Continental slope to open ocean

Oceans - Structure

• Oceanic Zone: Beyond continental shelf.– Epipelagic 0 - 200 m– Mesopelagic 200 - 1,000 m– Bathypelagic 1,000 - 4,000 m– Abyssal 4,000 - 6,000 m– Hadal 6,000 + m

• Benthic: Habitat on bottom of ocean.

• Pelagic: Habitat off the bottom of the ocean.

Neritic Zone – Over continental shelf

Oceanic Zone – From continental

shelf to open ocean

• Ocean Currents: movement of large masses of water

• Driven by steady winds, interrupted by land masses – Influenced by temperature + salinity

differences

• Gyres: large circular movements that circulate around an oceanic basin

• counterclockwise in southern hemisphere• clockwise in northern hemisphere

• What affects life in the ocean?• Light – only penetrates to upper few

meters• Nutrients – absorbed quickly by living

things – become limiting factor• Temperature• Salinity

– expressed as parts per thousand• 0/00

– Varies with depth, region (evaporation, fw inputs)

Marine Upwelling• Develop as winds bring nutrient rich waters to

surface• Along edges of continents, sea mounts and

islands• CA coastal regions: occur during summer

months driven by winds offshore• Nutrients stimulate food chain causing

massive increases in krill (tiny crustaceans)• Accounts for presence of sea bird and whale

populations in Monterey Bay through summer/fall

Carbon and oceanic waters

• CO2 dissolves in surface waters bicarbonate ions– Slow mixing with deeper waters

– Reaches equilibrium with atmospheric CO2

• Bicarbonate in water– Incorporated into organic compounds and

animal shells as CaCO3 & falls to bottom• Incorporated into rock (limestone sediments)

• Adds to carbon reservoir

• Acidification of surface waters

From wikimedia

From: http://www.climateoutcome.kiwi.nz/ocean-acidity.html

• Pteropods (winged snails) and ocean acidification

http://www.pbs.org/newshour/rundown/2013/09/little-creatures-big-impact.html

Temperature

• Stratification:– Sunlight waters warmer – less dense– Cooler waters are more dense– Thermocline: area of temperature transition –

between temperature strata

Nutrients in oceanic ecosystems• Less in euphotic zone due to scavenging

by phytoplankton• Greater below euphotic• Nutrients tend to be limiting

– Iron especially a factor

• Enrichment may lead to phytoplankton blooms

• Upwellings: bring nutrients in deeper waters to surface – stimulate entire food chain

Aquatic Food Chains and Pyramids

• An inverted pyramid – larger biomass in consumers than in producers– Populations able to increase rapidly

• Nutrient turnover much more rapid than in other ecosystems

• Producers short-lived - die or are consumed• Energy in producer level converted to biomass of

consumers

Deep-Sea Waters – no primary producers, rely on energy from photosynthetic activity of euphotic

• Little light penetrates beyond the top 300 meters

• Relatively few, bizarre, organisms live there

– Some fish have bioluminescent body parts

– Sea anemones use glass-sponge stalks to catch falling particles

• Hydrothermal vent systems (deep-sea vents) support a broad array of living organisms

– Autotrophic prokaryotes obtain energy by chemosynthesis

• Extract energy from hydrogen sulfide to manufacture food

–Live symbiotically within the tissues of heterotrophic animals

Summary – Marine Ecosystems• Various factors impact life in the ocean –

most limiting are light and nutrients• Marine ecosystems may be considered an

inverted pyramid, energy cycles quickly through system resulting in greater biomass of consumers than producers/prey

• Factors that introduce nutrients to marine systems result in rapid increase in growth/development of food web