shervette estuaries and benthic env fall08 student

shervette estuaries and benthic env fall08 student -...

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Unformatted text preview: Estuaries Defined • An estuary is a semi-enclosed coastal body of semiwater having free connection to the open sea at least intermittently, and within which the salinity is measurably different from the salinity in the adjacent open sea. • More simply: where _________ and _______ meet. Productivity • __________ alone has a 5-10 X higher net 5productivity than wheat. • Plant species richness can be ______, but biomass is _______. Organismal response to salinity Organismal • Motile organisms travel with the tide in the region that best suits them. • Stationary organisms are subjected to ______________ in salinity. • Upstream are freshwater organisms, downstream are saltwater organisms. • Some few species live in this boundary region. Formation of Estuaries • Often formed by a ___________ caused by longshore currents • Some formed by drowned river mouth (coastal plain estuary) • Deltas Salinity variation Salinity • Fresh water is lighter than saltwater and therefore flows over the top. • Coriolis effect also causes freshwater to flow closer to the coast on the north side. • A _______ of water where salinity changes rapidly from fresh to seawater moves back and forth with the tide. The communities of a tidal estuary The • • • • • • • Freshwater marsh Salt marsh Mud flats Open water Oyster beds and fringing oyster Mangrove wetland Seagrasses 1 Salt Marsh: Vegetational Zonation Vegetational • Eel Grass grows from low tide level to depths of 20 ft: 1) Has air spaces in blades for buoyancy and oxygen; 2) Provides substrate and food for many organisms • Cord Grass grows from mean high tide mark to low tide mark: 1) Hollow, air-filled stem to transport oxygen to airroots; 2) Salt glands; 3) C4 photosynthesis; 4) Nitrogen fixing bacteria in roots; 5) Contributes indirectly to productivity of the community by trapping detritus and sediments in root systems; 6) Very few organisms are equipped to eat Cord Grass. Eel Grass Animal inhabitants • Various arthropods, worms (tube worms, polychaete worms), and snails. • Pipefish (Syngnathus leptorhunchus) hides in Eel Grass and feeds on small crustaceans. • Salt-Marsh Harvest Mouse (Endemic and Salt- endangered to SF Bay); Builds a nest in the vegetation much like a bird and Is able to use saltwater as a water source. Cord Grass Brown pelican American Woodcock Resident Shore Birds of marshes in SC Resident • American woodcock • Anhinga • Black-necked stilt Black• Brown pelican • Common tern • Ring-billed gull Ring• willet Wading birds of South Carolina marshes (list not comprehensive) • American coot • Cattle egret (introduced/exotic) • Great Blue Heron • Great Egret • Green Heron • Lesser yellowlegs • Little Blue Heron • Snowy egret • White ibis • Wood Stork Willet Anhinga Black-necked stilt Laughing gull Great Blue heron Cattle egret American coot Great egret Little Blue heron White ibis Wood Stork 2 ___________ • When tide is in, mud-dwelling creatures mudbecome active • When tide is out, birds feed Mud flats _____________ • Primarily a detrital driven system. • Algae may provide some productivity in spring and summer. • Plankton and dissolved organic matter of secondary importance. • Oxygen levels in the mud often very low. The perspective of fishes and invertebrates ▬ Estuaries consist of a _________________________ Estuarine ecology, the study of habitatspecific nekton communities, and defining nursery habitats: Introduction Estuarine _________: Species that spend their whole life cycle within an estuary Estuarine _________ or estuarine ________ species: Rely on estuarine habitat during a particular life stage (usually as postlarvae and juveniles) ▬ In order for estuarine management practices to be effective, resource managers must understand how and when species utilize estuarine habitats Habitat _________________________ One of the most important characteristics of estuarine habitats for associated fauna Benefits of structure -Presence of structure is more important than type of structure -Enhanced/introduction of structural complexity increases prey survival -Disruption in flow creates area of deposition 3 Nursery habitat hypothesis • Fishery species that live and spawn in coastal waters have juveniles that migrate into estuarine nursery grounds where they grow into subadults • High levels of primary production • Few studies have defined species use of estuarine habitats and conclusively identify habitats that are essential in maintaining fishery production Examples of common species that Examples utilize estuaries as nurseries • White shrimp • Brown shrimp • Blue crab • Stone crab • Pinfish • Red drum (spottail bass) (spottail • Speckled sea trout Example of the concept of Estuaries as Nursery Habitat Benthic Communities Bat Stars in a Tide Pool Queen Charlotte Islands British Columbia Canada 4 Definitions And bacteria! •__________ includes all animals and plants that live on the ocean bottom •__________ - attached to the surface of hard structures or move along the sediment surface •________ - buried in the sediment or shells •_____________ - live along the bottom but occasionally move into the water column Global Distribution of Benthic Biomass Wet weight of benthic biomass. Note the correlation with regions of high primary productivity SeaWIFs Ocean Color – Global Primary Production Benthic environments include… include… Shallow, coastal environments – light reaches the bottom, benthic microalgae, macroalgae play a bottom, more dominant role in PP than phytoplankton; includes rocky intertidal, sandy intertidal, mud flats, continental shelves Deep-sea environments – _____________ is main Deepsource of PP; includes hydrothermal vents, methane gas hydrates, cold seeps, etc Most deep benthic communities are dependent upon the “rain” of particles from above. rain” megafauna [much bigger than 1 mm] (Historically, focus has been on the larger organisms (why?), but the protozoa and bacteria are extremely abundant and often dominate overall benthic metabolism) General Description • The benthos is highly-diverse - about 98% of all marine species are found in benthic habitats • The type of substrate (rock, sand, mud, etc.) determines the community composition • Many species are highly adapted for living in specific habitats • The distribution of benthic biomass is patterned after the distribution of primary productivity in the surface waters • Zonation - the spatial distribution of species into different habitats - is an important aspect of benthic species and communities • Distribution patterns may be random, uniform, or clumped; clumped patterns are most common in nature King Penguins on South Georgia Island Incubating their eggs An example of a near Uniform Distribution in nature Sampling the benthos Non-invasive: __________ Non• Good for long time series studies • Allow characterization of movements and sea floor dynamics • Not as quantitative, less useful for process studies (rate measurements) 2°N, 140°W Sea urchin tracks Fish swarming bait 5850 m NW Pacific 5 Smith-McIntyre Grab Invasive: Dredges, trawls, grabs • Destructive, but quantitative • Grabs allow characterization of sediment (grain size, organic content, porosity, etc) • e.g. Smith-McIntyre grab: Springdriven paired scoops suspended from lever arms; may disturb sediment with pressure waves as they close; or fail to close Shallow Water Benthic Environments Sandy shores Rocky Intertidal Seagrass beds Salt marsh Box corers Stainless steel box, open at both ends Driven into the sediment by weights Release-triggered blade swings down, Slices through sediment to close box Open on top Animals of Rocky Shores Intertidal Zone - the area between the high tide and low tide line along the shore (tidal extremes) Oyster Reefs Organisms in the supralittoral zone (Spray Zone and High Tide Zone) tend to be tolerant of a wide degree of temperatures, resistant to desiccation, resistant to strong wave forcing. Are often characterized by strong holdfasts/feet, shells that will seal tightly, or are motile and thus able to escape suboptimal conditions. Main zones are the spray, high tide (supralittoral), middle tide (midlittoral), and low tide (lower littoral). Very stressful habitat - organisms stratified according to their tolerance to environmental stress Due to the periodic immersion and emersion, rapid changes occur in: • water cover • oxygen • temperature • air exposure • salinity • water turbulence Tide Pools on Rocky Shores The Midlittoral Zone (Middle Tide Zone) – Note general lack of burrowing organisms. 6 The Lower Littoral Zone (Low Tide Zone)- softer bodies, fewer adaptations to extremes • Primary producers in rocky intertidal environments are mostly macroalgae • “Seaweeds” are multicellular algae, not Seaweeds” true plants (Protista) (Protista) % organic matter content increases as depth increases, i.e. the bottom is softer the deeper you go Macroalgae are important primary producers, also provide habitat or nursery areas for fish, invertebrates • Are photosynthetic, occur in a wide variety of shapes and sizes (largest can reach 60 m long or more) • Nearly 7000 species have been identified • Have strong holdfasts, are stream-lined, streamflexible bodies, slimy (helps hold in water); require a substrate for attachment Seaweeds: are usually anchored to a substrate, take up nutrients from the water, are adapted to resist desiccation during tidal exposure (waxy coatings) e.g. Kelp forests (cold water, wind-swept coasts) provide food and shelter e.g. Seaweeds on rocky shores are grazed by sea urchins, snails Mature Macrocystis bed @ 60’ No extensive support structures and roots like terrestrial plants Fucus Animals of Sediment-Covered Shores Sediment- Subtidal Beach Fauna •These habitats are often called soft substrates •Is a lower energy environment (less currents and wave action) Have a lower diversity of macrofauna •Higher percentage of organisms burrow into the sediment to prevent desiccation or avoid predation (compared to rocky intertidal) Habitat Types and Environments Beaches Salt Marshes Mud Flats Seagrass Beds 7 ____________________ ______________________ •Shallow subtidal zone of the coastal environment •Areas of high productivity and are important to fish and other organisms as a direct or indirect source of food •Other fish find their food in these habitats by feeding on detritus from detritus decomposing leaves, invertebrates, small fish, and/or shellfish that can be found attached to their leaves or living within the plants. plants. •Provide living space, refuge from predators, and essential nursery areas to commercial and recreational fishery species and to a great number of invertebrates •Stabilize sediment; can diminish the effects of strong currents, providing protection to fish and invertebrates and preventing the erosion of bottom areas. Thalassia testudinum • Transitional areas between land and water mainly in temperate, boreal regions • Heavily influenced by tidal forcing, freshwater inflows • Buffer erosive physical forcing, filter excess nutrients and sediments • Microbial activity important • Provide habitat, nursery grounds for fish, crabs, shrimps, molluscs _________________ Suspension Feeders – sweep organic matter from the water (detritus or live material), e.g. barnacle (below) Deposit Feeders - engulf sediment and process it in their guts to extract organic matter; Worms (nematodes & polychaetes), sea urchins, some clams cirri Shallow Offshore Animals ________________ • Have the greatest known species diversity in the marine environment • Sort of a tropical rain forest in the sea • Have 25% of all known marine species • Require warm waters (restricted to the tropics, >18° C) • Live in oligotrophic waters (low nutrient concentrations) • Clear waters free from suspended particulates • Found in relatively shallow waters (most coral species require light) • Must grow on a firm substrate The Great Barrier Reef Australia Global Distribution of Coral Reefs 8 Seasonal and spatial variation in nekton communities of oyster and marsh habitats in a Mississippi estuary Importance of oyster and nvb habitat Importance of vegetated marsh Oyster reefs support distinct assemblages of decapod crustaceans Higher growth rates in Spartina marsh edge habitat when compared to adjacent habitats Important ecological component of estuarine habitats High survival rates in salt marsh habitats Mechanisms underlying the importance of oyster habitat include increased survival and greater forage availability Nonvegetated bottom habitat supports many estuarine species Drop sampling Fish abundance and diversity Measured temperature (°C), salinity (PSU), and dissolved oxygen (mg/L) using a YSI 85 meter and water depth (cm) using measuring tape 633 individual fish; 41 taxa in 22 families In vme habitat, removed marsh vegetation from the sampler and recorded the number of stems 27 species in oyster, 9 exclusively In oyster habitat, percent oyster cover was recorded Nvb: C. boleosoma,G. bosc, Leiostomus xanthurus All oyster washed and organisms present were collected 28 species in vme, 13 exclusively 13 species in nvb, none exclusively Vme: Gobiosoma bosc, Ctenogobius boleosoma, Fundulus grandis Oyster: G. bosc, L. xanthurus, C. boleosoma Photos by “Tino” 9 Invertebrates Diversity and Richness 2734 individuals marsh 2.42 0.61 52 Diversity Evenness Richness 24 taxa in 11 families Habitat nvb 2.71 0.85 24 oyster 2.57 0.66 49 Oct 2.43 0.63 46 Season May 2.80 0.79 34 Jul 2.33 0.61 46 Sampling Area Heron Crooked 2.42 2.61 0.64 0.67 45 48 22 species in vme, 3 exclusive 10 in nvb, none exclusive 20 in oyster, 2 exclusive 120 marsh nvb oyster 12 marsh nvb oyster 100 10 8 Mean density Richness (no. of species) 14 6 4 2 80 60 40 20 0 Fall Spring Conclusions To determine the relationship between three common shallow estuarine habitats (oyster, vme, and nvb) and nekton community structure Documented three basic trends related to the importance of oyster and vme habitats: 1) Oyster and vme provide habitat for significantly more species relative to nvb; 2) Oyster and vme provide habitat for uncommon and rare species; and 3) Several species collected across multiple habitats occurred at higher abundances in oyster or vme habitat Summer 0 Fall Spring Summer Oyster, similar to vme and submerged aquatic vegetation, may provide higher growth rates for some species and refuge from predation for others. Oyster appears to support a temporally diverse and spatially distinct nekton community and deserves further attention in research and conservation. Contrary to the current low value ranking of oyster habitat relative to other estuarine habitats, oyster provides higher quality habitat for many species. 10 ...
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