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Soft Bottom Grain Sediment, Mud, and Sand (...Yipee!) Soft Bottom grain sediment, mud, and sand (...yipee!) Global distribution • LARGEST BENTHIC HABITAT IN THE WORLD! • 60% of Earth’s surface • Grain sediments, mud, sand • Biodiversity and productivity vary depending upon depth, light exposure, temperature, sediment grain size and abundance of microalgae and bacteria. Sedimentary plains Snelgrove 2010; Ausubel et al. 2010 Foundation species ● Snails ● Clams ● Urchins ● Sand dollars ● Worms ● Sea stars ● Shrimp ● Meiofauna *Not all substrate is made equally Trophic Structure -Dominated by infaunal invertebrates: -Common epifauna: -Benthic primary producers: Ecological Functioning--Bottom-Up vs Top-Down ’Fluid’ unconsolidated sediment turnover maintains diversity Predation maintains variability in the distribution of organisms (Olafsson et al. 1994) Direct competition for food/space is rare Ecosystem services Soft-sediment communities: -Seagrass grows in soft-sediment -Sequester C (blue carbon) -Commercial fisheries Threats to the ecosystem Ecological Insights Carbon sink hypothesis Physical disturbance shapes diversity - (linked to IDH) Predation maintains variability in the distribution of organisms (Olafsson et al. 1994) Summary -Largest benthic habitat in the world -Biodiversity and productivity vary depending upon depth, light exposure, temperature, sediment grain size and abundance of microalgae and bacteria -Dominated by infaunal organisms, but support habitat for important fisheries -Major carbon sequestration! Polar marine ecosystems Global distribution Arctic Ocean - largely land-locked - extensive shallow shelf seas influenced by seasonal air and freshwater fluxes from surrounding continents - permanent cover of slowly circulating ice floes surrounded by seasonal pack ice - Seasonal fluctuation in ice cover: 14x106 km2 to 7x106 km2 Global distribution Antarctic Ocean - Narrow, deep continental shelf with continuous circulating Southern Ocean current - Continent is surrounded by extensive seasonal fluctuation in ice cover (red line) Foundation species - 5% of Southern Ocean primary production by phytoplankton in sea ice - But fuels food web supporting many other organisms (microbes to small invertebrates) trapped in ice - As ice thaws, these invertebrates and algal blooms are important source of concentrated food for pelagic species when production is otherwise sparse - Krill fuel pelagic food webs in Antarctic pelagic food webs - Diversity of benthic suspension feeders (sponges, cnidarians, bryozoans, tunicates)and some macroalgae create three dimensional structure in the benthos - Arctic cold water corals an important source of physical structure Trophic structure Arctic food web Seasonal variation in primary production driven (limited) by great variation in daylight length Benthic communities (soft bottom) dominated by suspension feeders Strong pelagic-benthic coupling Darnis et al. Climatic Change (2012) Ecological Functioning--Bottom-Up vs Top-Down Sea ice, anchor ice and icebergs scrape the bottom (to 300m depth) and a major source of disturbance to benthic communities Because of high and variable plankton production (especially krill in Antarctica) community structure and dynamics is largely bottom-up Ecosystem services Provisioning - Fisheries (commercial – Arctic and Antarctic) - Fisheries (subsistence – Indigenous - Arctic) - Fossil fuels (Arctic) Regulating - Cold water global conveyor - Carbon sequestration - Sea level regulation Cultural - Fisheries and environmental - Spiritual - Polar bears and penguins Threats to the ecosystem 1) Global climate change shrinking sea ice cover - increases vessel traffic and oil exploration - habitat loss for marine mammals (e.g. polar bears) - loss of human access to marine mammals Threats to the ecosystem 2) Overfishing - Fish in Arctic and Antarctic - Krill and whales in Antarctic Ecological Insights Foundation species (Dayton 1972) “Species of particular importance to the structure of a community” Subsequently applied to species that contribute importantly to physical structure and productivity of a community. Examples: the sponges and corals that create physical habitat for other species on an otherwise featureless seafloor Ecological Insights Benthic-pelagic coupling The critical role of pelagic production (including associated with sea ice) that fuels the great diversity of benthic detritivores and planktivores, which in turn are consumed by higher trophic levels. Similar to deep sea benthic ecosystems. Illustration by Jack Cook (WHOI) Summary - Constrained to poles by water temperature and ice - Sea ice has huge influence on ecosystem - Arctic and Antarctic very different (continental land mass, depth of seafloor) - Critically important “foundation” species - Largely bottom-up trophic and community structure - Strong pelagic-benthic coupling fuels benthic community structure and food webs - Greatly impacted by global warming Pelagic ecosystems Global distribution Pelagic = of, relating to, or living or occurring in the open sea Pelagic ecosystems represent 99% of the total biosphere A.K.A. “The sunlight zone” (euphotic zone) A.K.A. “The twilight zone” To be covered in Deep sea module 71% of Earth is covered by oceans. Neritic zone – defined from the coast to the edge of continental shelf (~200m depth). Represents 8% of total ocean. Oceanic – the vast open ocean, the largest living space on earth. Foundation species - Primary producers – marine phytoplankton (largest to smallest; Diatoms, Dinoflagellates, Prymnesiophytes, Cyanobacteria, Prochlorophytes). - ~½ of every breath of oxygen is produced by marine phytoplankton. - ~1/5 of every of breath of oxygen is produced by marine diatoms. - Marine zooplankton comprise ~7,000 described species across 15 phyla (Bucklin et al., 2010 – Oxford: Blackwell Publishing Ltd.) - Mesopelagic fishes represent the most abundant assemblage of vertebrates on Earth with an estimated total biomass of ~15,000 million tons. The most abundant vertebrate on earth is the mesopelagic bristlemouth (Cyclothone spp.) with hundreds of trillions of individuals. Trophic structure Trophic structure In the ocean, high turnover of primary producers generates an inverted biomass pyramid. Ecological Functioning--Bottom-Up vs Top-Down - In the ocean, primary production is limited by nutrient availability (primarily nitrate (NO3) and iron (Fe)). - Unlike land where nutrients are readily available beneath the soil, the ocean, with an average depth of 4,000 meters (~13,000 ft.), has the bulk of its nutrients far beneath the euphotic zone where primary production cannot occur. Physical processes (i.e. wind-driven circulation, tidal mixing, etc.) transport nutrients to sunlit surface waters - For this reason, pelagic ecosystems are largely believed to be controlled by bottom-up processes (i.e. food limited; e.g. McGowan et al., 1998). - However, we know that fishing vastly restructures pelagic marine ecosystems, and therefore top-down processes also operate (). - But, in some cases “wasp-waist” control also proliferates (Cury et al., 2000 ICES JMS) Ecological Functioning--Bottom-Up Ecological Functioning--Top-Down Ecological Functioning—Wasp-Waist Ecosystem services - Shipping – estimated annual value of 1.3 trillion USD. - Fisheries - both marine capture and aquaculture production totaled to 110 mmt in 2016. - Oxygen production – every other breath of oxygen is generated from the ocean. - Carbon sequestration – every year, ¼ of carbon emitted through the burning of fossil fuels is absorbed by the ocean. - Biogeochemical cycling (e.g. the Sulphur cycle) - Global climate regulation - Existence value – e.g. the unquantifiable value of the existence of blue whales Threats to the ecosystem - Overfishing - Pollution (e.g. microplastics and mercury pollution). - Warming - Changes to ocean currents breakdown of eastern extent of Gulf Stream = more severe winter conditions in western Europe. - Ocean Acidification Ecological Insights - Marine fish populations dynamics are highly irregular, depend on recruitment strength, which is driven by changes in food availability and current (Hjort, 1914, and citing studies). - The structure and function of marine ecosystems respond drastically to inter-annual changes and inter-decadal climatic variations (McGowan et al., 1998 Science) - The “False Bottom” and diel vertical migration (largest migration on Earth). Summary - The pelagic ecosystem is 99% of Earth’s biosphere. - ½ of Earth’s oxygen is generated in the pelagic environment. - Largest vertebrate assemblage on Earth. - Largest migration (daily!!!) on Earth! - High turnover of primary producers inverted biomass pyramid. - Ecosystem structure is driven by bottom-up, top-down and wasp-waist processes. - Highly dynamic ecosystem, driven by interannual, inter-decadal and secular climatic events and anthropogenic impacts. Deep Sea Global distribution A.K.A. “The sunlight zone” (euphotic zone) A.K.A. “The twilight zone” Deep sea Deep sea = dark sea anywhere from 200 to 1000m and below (depending on who you ask). Conditions in the deep sea PRESSURE!! 500 atmospheres - around the weight of 48 jumbo jets on the abyssal plain Constant environment: Dark no diurnal light pattern Salinity Temperature ~2C O2 saturation Foundation species = worms!! - Primary producers – None! Well not exactly but no photosynthesis - Primary source of food is marine snow and carcass falls - Detritivores rule! Many of the species known to science scavenge ○ Much of the data collected from baited camera traps - Only primary production from chemosynthesis
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