Lect10
Marine Ecosystems
Lect07
Marine Ecosystems
•
•
•
•
Estuaries
Marine Shores
Shallow Marine Waters
Oceans
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
– Mesopelagic
– Bathypelagic
– Abyssal
– Hadal
0 - 200 m
200 - 1,000 m
1,000 - 4,000 m
4,000 - 6,000 m
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/rundo
wn/2013/09/little-creatures-bigimpact.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