Estuaries and Ocean life

Estuaries:

Defining Coastal Regions:

  • Shore: Zone between low tide and highest area on land affected by waves

  • Coast: Extends inland as far as ocean related features are found

  • Coastline: boundary between shore and coast

    • Highest area affected by waves 

Coastal Waters:

  • Relatively shallow waters overlying continental shelf 

  • Adjoin continent or islands

  • Influenced by river runoff, winds, tides

  • Open ocean lies beyond

  • Anything beyond coastal waters = open ocean

Salinity in Coastal Waters:

  • Halocline: Area where salinity changes rapidly (shift in salinity with depth)

    • Runoff: low to high (addition of fresh water to ocean water, fresh water can float on top of ocean water if nothing mixes it in)

    • Dry offshore wind: High to regular salinity (fuels evaporation, fresh water is evaporating leaving salts behind)

    • Creates coastal front

  • Isohaline: area where salinity is mixed rapidly (says normal)

Temperature in Coastal Waters:

  • Impacted by:

    • Winds

    • Insolation

    • Currents

Thermoclines:

  • A layer of rapidly changing temperature

    • Can sometimes be seen, can definitely be felt

    • Warm at surface, cooler down deep

Estuaries:

  • Partially enclosed body of water in which freshwater runoff dilutes ocean water

  • Highly productive marine ecosystems

    • Mouth: area with exchange of seawater

    • Head: 

Classification:

  • Geographic Origin: 

    • Coastal Plain Estuary: formed when an eroded river valley is flooded with seawater as sea level rises

      • Ex: Chesapeake Bay

    • Fjords: Formed glaciated valley now flooded with seawater

      • Alaska

    • Bar Built Estuaries: Lagoon separated from ocean by sand bar or barrier island

      • Outerbanks

    • Tectonic Estuaries: Faulted or folded down dropped area now flooded with ocean

      • San Francisco Bay

  • Water mixing regime:

Models of water mixing in Estuaries:

  • Salt wedge:

    • High volume river

    • Surface fresh from head to mouth

    • Salinity gradient at depth (horizontal and vertical)

  • Slightly stratified

    • 2-level flow

    • Upper layer less salty; lowe layer more salty

    • Estuarine circulation: Mixing by wind and tides

  • Vertically mixed:

    • Shallow

    • FW input low volume

    • Net flow head to mouth

    • Wind and tidal mixing

    • Horizontal change in salinity

  • Highly stratified: found only in fjords

    • Deep

    • Surface salinity increases

    • Bottom salinity uniform

    • Relatively strong halocline

    • Entrainment at interface

Negative Estuary:

  • Low to no river

  • High evaporation

  • Salinity in upper layer decreases towards mouth 

  • Salinity in lower layer increases towards head

  • Vertical salinity profiles show gradual increase from the surface to the bottom

  • Ex: Laguna Madre

    • Long barrier island with two narrow inlets

    • Formed about 6000 years ago

    • Large temperature range

    • Hypersaline

      • High evaporation

    • Marsh replaced by open beach sand on Padre Island

Daily patterns:

  • Dominated by tidal flushing

  • Influenced by Coriolis effect, N hemisphere

  • Flood currents flow on “right side” (east)

  • Ebb currents on “left” (west)

  • Isohalines slosh with tides

Coping with change:

  • Living organisms must adapt to oscillations in:

    • Salinity

    • Oxygen 

    • Temperature

    • Suspended sediment

    • Light

Seasonal Patterns

  • Dominated by spring freshness or other fluctuations in FW input

  • Stratification and circulation patterns change with the seasons

  • Can cause anoxia and fish kills

Wetlands:

  • Margins of estuaries and other coastal areas support wetlands

  • Wetlands: Ecosystems with water table close to surface

  • Two most important types of coastal wetlands:

    • Salt marshes: mostly grasses (mid-high latitudes)

    • Mangrove forests (low latitudes)

Value of Marshes:

  • Important habitat

  • Nurseries for more than ½ of commercially important fish in SE US

  • Help preserve water quality

Life in the Ocean:

Book’s Definition of life:

  • Living things can (needs all 4)

  1. Capture store, and transmit energy (feeding and respiration)

  2. Reproduce

  3. Adapt to environment

  4. Change over time (homeostasis) 

What is the meaning of life:

  • Find food 

  • Avoid being eaten 

  • Reproduce 

    • Purpose of all living organisms: to find food and avoid being eaten long enough to reproduce

      • These require many adaptations to have formed

Taxonomic Classification:

  • Carolus Linnaeus -1758:

  • Studied nomenclature

  • Developed basis of modern classification of organisms

    • Wrote systema naturae (Plant and animal classification book 2,300 pages long)

  • Conventions from Linnaeus: 

    • Taxa

    • Binomial nomenclature (how each living organism is recognized across the world)

  • Taxonomy: systematic classification of organisms

    • Tells the story of all life on earth

    • All living things have a common ancestor

    • Physical characteristics

    • Genetic information

  • Phylogenetic tree:

    • Represents the evolutionary relationship for all living organisms

Three Domain System:

  • Bacteria: simple life forms usually without nucleus

  • Archaea: simple, microscopic creatures; many extremophiles (flourish in extreme environments)

  • Eukarya: complex organisms with nucleus; plants, fungi, animals, and protists

Taxonomic Hierarchies: (don't need to memorize, but recognize that it exist with multiple levels as a way to classify organisms)

  • Kingdom: 

    • Protista: Heterotroph and autotroph

    • Fungi: Heterotroph

    • Plantae: Autotroph

    • Animalia: Heterotroph

  • Phylum

  • Class

  • Order

  • Family

  • Genus

  • Species 

    • Fundamental unit

    • Population of genetically similar, interbreeding individuals

Other classification schemes:

  • Behavior:

    • Plankton (floaters)

      • Drift with the currents (not strong enough to swim against currents)

    • Nekton (swimmers)

  • Habitat:

    • Benthic (bottom)

      • Benthos 

    • Pelagic (water column)

    • Neritic (shallow areas <200 m)

    • Oceanic (deeper areas >200 m)

  • Function:

    • Primary producers

    • Consumers

    • Predators

Number of Marine Species:

  • More land species than marine species (86% on land and 14% in the ocean)

    • Based on number of types of organisms

    • More diversity on land because conditions vary dramatically forcing species to adapt tp micro climates and seasons

  • Ocean has relatively uniform conditions

  • Less adaptation required, less speciation

  • Marine species overwhelmingly benthic, on or in the sea floor, (98%) rather pelagic

Stability and Change

  • The marine environment is more stable than land

    • Temperature does not fluctuate

    • Dark, cold, and experiences high pressure

    • Organisms have evolved to match the oceans conditions

  • Organisms in the ocean are less able to withstand environmental changes

Maintaining Position in a Fluid Environment:

  • Need to be where food and mates are

  • Photosynthetic organisms need to be near the surface where there is light

  • Most adaptations relate to viscosity

    • Warm water lower viscosity, Cold water higher viscosity (way of defining how thick a fluid is; Ex: honey is more viscous than water)

    • Higher salinity higher viscosity, Lower salinity lower viscosity

  •  Organisms that actively swim need to conserve energy

Ratio of Surface area to volume:

  • Buoyancy best high SA:V (increased buoyancy = increased SA:V)

    • Small size

    • Appendages

  • SA:V impacts:

    • Gas exchange 

    • Nutrient uptake

    • Excretion of waste

Buoyancy:

  • Resistance to sinking

    • Appendages (increase surface area)

      • Fewer in cold

      • More in warm

    • Smaller size

    • Oil in some, esp. Micro organisms

    • Gas chambers, bladder, pneumatocysts

Resistance to sinking: Copepods

  • Oithona setigera

  • Gaussia princeps

Viscosity and swimmers:

  • Viscosity of water can hinder swimmers

  • Instead of needing to increase resistance to avoid sinking, then need to reduce friction and turbulence in the water as they move through it 

  • Water must be displaced in front

  • As water moves back into place behind, creates turbulence

  • Streamlining reduces drag (nearly all active marine swimmers have a streamlined body shape)

Streamlining:

  • Shaped with least resistance to fluid flow

  • Flattened body (side to side, like a swordfish, or dorsally, like a sea turtle)

  • Tapered back end (rounded along the front)

Adaptations for fast swimming:

  • Nearly ideal streamline

  • Stiff narrow fins

Adaptations for fast swimming: Warm Muscles

  • Counter- current

  • Circulation transfers

  • Heat in rete mirabile

    • Specialized structures that use countercurrent circulation and blood vessels that are close enough together that they can exchange heat or chemicals

    • Keeps swimming muscles warmer than the outside ocean

    • Countercurrent blood flow is also used in the gills and other organs to facilitate the exchange of dissolved gasses and waste

Ocean Temperature

  • Narrow range, small variations (daily, seasonally, annually)

  • Deep ocean is nearly isothermal, larger range in coastal areas

  • Ocean temperatures more stable than on land (does not change quickly due to high specific heat capacity)

    • Higher solar radiation does not penetrate to deep ocean layers

    • Warming reduced by evaporation

    • Mixing

Temperature and Marine Organisms:

  • Stenothermal

    • Organisms withstand small variation in temperature

    • Most in open ocean at depth

    • Some in tropics or polar regions

  • Eurythermal

    • Organisms withstand large variation in temperature

    • Many in coastal waters

    • Most large swimming organisms

Cold vs Warm Water Species:

  • These are generalization, not hard and fast rules

    • Plankton (floating organisms) are smaller in warmer regions and have more appendages

    • Tropical organisms grow faster, live shorter lives, and reproduce more often than cold water organisms

    • More species in warmer seawater

Accessory Pigments

  • Important in the use of satellites to detect organisms in the ocean

Salinity and Osmoregulation:

  • Osmoregulators regulate the concentration of salts in cells or bodies

  • COncentration of salt in seawater higher than in cells

  • Diffusion goes from areas of high concentration to low

  • Salts cannot easily diffuse across cell membrane, but water can

  • Most organisms in sea continually lose water

  • Must either prevent loss or replace it

Marine Fishes:

  • Concentrate small amino acids and other charged particles to raise the salinity of their tissues to about 14%

    • Water loss by osmosis through gills and skin

    • 35% salinity outside the fish (in the ocean)

    • Fish are constantly drinking seawater

  • Salts is excreted by gills

  • Conserve water by not urinating much (small volume of relatively salty urine)

  • Salts pass through gut

Salinity and Plants:

  • Waxy leaves are tough and succulent

  • May concentrate salt in leaves and drip (drop when they get to salty)

  • Some use salt glands to excrete salt

    • Along stems and leaves

  • Some exclude salt at roots (reverse osmosis)

    • Specialized glands/adaptations

Dissolved Gases:

  • Animals extract dissolved O2 from seawater through specialized organs: Branchiae, gills, integument, respiratory trees

    • Many animals can take up oxygen through their skin

  • Gases dissolve in cold water very well

    • Oxygen enters water at the surface

    • Bottom water formation brings oxygen down to the seafloor

    • Needs to come back up to the surface to be reoxygenated

  • Exchange of O2 and CO2 directly with seawater

  • Branchiae/gills structure and location varies among animals

  • Low marine oxygen levels can kill

Fish:

  • As fish swim and respire water flows into the fish's mouth, over the gills, and into the operculum

    • Blood moves in opposite direction

  • Blood vessels and seawater

Reproduction:

  • Some reproduce asexually, but nearly everything needs some sexual step to replicate and have biodiversity

  • Sexual reproduction in the ocean has to happen in a fluid

  • Broadcast spawning: eggs and sperm released into seawater (mix outside the body and develops on its own)

    • Most used

  • Brooding: eggs/young protected

Avoiding Predation:

  • Seen on land:

    • Disruptive coloring: Coloration that confuses predators, allows the organism time to escape

    • Camouflage: Color and texture of organism matches its environment

  • Not seen on land:

    • Transparency: vertically no coloration (very difficult to see)

    • Countershading: When an organism is dark on the top and white on the bottom

      • Bright white belly helps the organism blend into the brightness of the sun at the surface 

      • If look down at fish, it blends in with the seafloor

      • About the perspective of the predator

Behavioral Adaptations for Avoiding Predation:

  • Mutualism: both benefit from a situation (live together)

  • Commensalism: One benefits and the other is neutral

  • Parasitism: One benefits, the other is harmed

  • Schooling: Where smaller organisms aggregate in a group, making it look like a larger organism

    • Confuses predator

Avoiding Predation: Vertical Migrations

  • Deep Scattering Layer: Layer of organisms in the ocean, 1000 m deep to surface (diheal migration)

    • Concentration of small organisms

  • Daytime: down 1,000 meters (hiding in the dark part of the water column)

  • Nighttime: Close to surface (

  • This layer migrates up and down everyday

  • Allows them to avoid daytime predators at the surface

  • Mammals can hunt without sight (crepuscular (active at dawn and dusk) and nocturnal can still prey on this migrating layer)