Aquatic Ecology

Objectives Discuss biodiversity and endangered species. Examine the needs of all aquatic environments. Discuss the three types of aquatic environments. Identify various zones in a lake. Analyze the trophic stages of a pond, lake, or

stream. Discuss and define biological indicators.

List sensitive and tolerant groups. Describe how to collect samples. Identify macro invertebrates in your sample.

Identify and determine the quality of a local stream.

BIODIVERSITY PROTECTION Hunting and Fishing Laws

By 1890’s, most states had enacted some hunting and fishing laws. General idea was pragmatic, not aesthetic or moral

preservation. White-tailed deer Wild turkeys Wood ducks

Endangered Species Act Established in 1973.

Endangered are those considered in imminent danger of extinction.

Threatened are those likely to become endangered, at least locally, in the near future. Vulnerable are those that are naturally rare or have been

locally depleted to a level that puts them at risk.

Endangered Species Act Cont’d ESA regulates a wide range of activities involving

Endangered Species: Taking (harassing, harming, pursuing, hunting, shooting,

killing, capturing, or collecting) either accidentally, or on purpose.

Selling Importing into or Exporting out of the U.S. Possessing Transporting or Shipping

Endangered Species Act Cont’d Currently, the U.S. has 1,300 species on its

endangered and threatened lists, and 250 candidate species waiting for consideration. Number reflects more about human interests than actual

status. Invertebrates make up 75% of all species, but only 9%

worthy of protection. Listing process is extremely slow.

Recovery Plans Once a species is listed, USFWS is required to

propose a recovery plan detailing the rebuilding of the species to sustainable levels. Total cost of all current plans = $5 billion.

Opponents have continually tried to require economic costs and benefits be incorporated into planning.

Reauthorizing ESA ESA officially expired in 1992.

Proposals for new ESA generally fall into two general categories: Versions that encourage ecosystem and habitat protection rather than

individual species. Safe Harbor policies that allow exceptions to critical habitat designations.

(Economic Considerations)

What are the basic needs of aquatic biota?

CO2 O2

Sunlight Nutrients- food &

minerals

What factors influence the availability of those basic needs?

Substances dissolved in water- Nitrates, phosphates, potassium, O2

Suspended matter- (silt, algae) can affect light penetration

Depth Temperature Rate of flow Bottom characteristics

(muddy, sandy, or rocky) Internal convection currents Connection to or isolation

from other aquatic ecosystems.

Types of Aquatic Ecosystems Freshwater Ecosystems

Standing Water- lakes & ponds

Moving Water- rivers & streams

Transitional Communities Estuaries Wetlands- bogs/fens,

swamps, marshes Marine Ecosystems

Shorelines Barrier Islands Coral Reefs Open Ocean

Types of Aquatic Systems

Lakes & Ponds

Rivers & Streams

Wetlands

Estuaries

Marine system

Groundwater

Freshwater Ecosystems Usually 0.005% salt

Some exceptions: Great Salt Lakes-

5-27% salt Dead Sea- 30% salt

Moving water- high elevations; cold; high O2; trout; streamlined plants

Standing water- lower elevations; warmer; less O2; bass, amphibians; cattails, rushes

Lentic Zones

Lotic Environments

Lotic Environments

Lakes and Ponds Critical differences from

other freshwater systems Longer residence time Typically not shaded

with most of the surface area exposed to sunlight

Florida lakes are typically shallow and well mixed

Florida lakes are often highly colored, but can have light reaching much of the bottom

Photo by Bill Wade

Watershed / Lake Area Ratio

Watershed area relative to lake area will influence the residence time of water in the lake.

This ratio is also a factor in the nutrient loading to the lake

Lake Habitat Zones

Oligotrophic Northern Lake

Eutrophic Southern Lake

Lake Littoral Zone Functions

Intercepts Nutrients Refuge from Predators Nursery for Fish

Lake Limnetic/Pelagic Zone Functions

Plankton Zooplankton

Submerged Aquatic Vegetation (SAV) Nutrient uptake Sediment stabilization Habitat Oxygen production

Lake Limnetic / Pelagic Zone

Pond Food Web

Nutrients

Algae/Plants

Grazers

Fish

Nutrients Algae/Plants Grazers Fish

Relationship Between Nutrients and Pond Productivity

Nutrients Algae/Plants Grazers Fish

Nutrients Algae/Plants Grazers Fish

Nutrients Algae/Plants Grazers Fish

Nutrients Algae/Plants Grazers Fish

NutrientsHabitat/Environmental Impacts

Algae/Plants Grazers Fish

Low nutrientsLow primary productivityLow grazers and insectsLow fish production

Clear waterSandy/low organic matter on bottom

TROPHIC STATEModerate nutrientsIncreased primary productivityMore grazers and insectsMore fish production

Moderate water clarity More aquatic plantsSome organic sediment accumulation

TROPHIC STATEHigh nutrientsHigh primary productivityLarge number of grazers and insectsModerate fish production

Low water clarity, or Clear with aquatic plantsHigh organic sediment accumulation

Trophic State Change Nutrients & Productivity Sediment &

Accumulation Species Shifts Species Richness

How is a lake stratified and what lives in each level?

Epilimnion- upper layer of warm water; high light & O2; ex: water striders, phyto- & zooplankton, fish

Thermocline (mesolimnion); middle layer; medium light & O2; ex: phyto- & zooplankton, fish

Hypolimnion- lower layer of cold water; lower light & O2; ex: fish

Benthos- bottom level; no light & little O2; ex: anaerobic bacteria, leeches; insect larvae

Littoral- near the shoreline; cattails, rushes, amphibians, etc.

Transitional Communities ESTUARIES Where freshwater

dumps into ocean Brackish (less salty

than seawater) Has rich sediments

that often form deltas Productive &

biodiverse Organisms adapted to

varying levels of salinity as tide ebbs & flows

“Nursery” for larval forms of many aquatic species of commercial fish & shellfish

Transitional Communities WETLANDS Land saturated at least part of

the year Swamps- have trees like bald

cypress; high productivity Marshes- no trees; tall

grasses; high productivity Bogs/Fens- may or may not

have trees; waterlogged soil with lots of peat; low productivity Fens- fed by groundwater &

surface runoff Bogs- fed by precipitation

Bog

Fen

Marsh

Swamp

Importance of Wetlands Highly productive- get lots of

sunlight, ↑ plants = ↑ animals Nesting, breeding ground for

migratory birds Slows flooding by absorbing runoff Silt settles, making water clearer &

nutrient rich Trap & filter water Natural chemical rxns neutralize

and detoxify pollutants Gives H2O time to percolate thru

soil & replenish underground aquifers.

Threats- artificial eutrophication (see slide 13), draining, sedimentation via construction

“Nature’s Septic Tank”

Marine Ecosystems SHORELINES Rocky coasts- great density &

diversity attached to solid rock surface

Sandy beaches- burrowing animals

Threats- due to hotels, restaurants, homes on beach, more plant life destroyed, destabilizing soil, susceptible to wind & water erosion

Insurance high; danger of hurricanes, erosion

Build sea walls to protect people but changes & endangers shoreline habitat

Marine Ecosystems BARRIER ISLANDS Low, narrow offshore

islands Protect inland shores

from storms Beauty attracts

developers = developers destroy land

New coastal zoning laws protect future development

MARINE ECOSYSTEMS CORAL REEFS Clear, warm shallow seas Made up of accumulated

calcareous (made of calcium) skeletons of coral animals

Formation depends on light penetration.

Have a symbiotic relationship with algae

Very diverse, abundant (rainforests of sea)

Threats- destructive fishing (cyanide & dynamite to stun fish), pet trade; about 3/4ths have been destroyed

What factors can alter aquatic ecosystems?

Natural Succession- normal cycle of pond becoming forest

Artificial Succession- humans add N & P to water via fertilizer & sewage causing succession to happen faster = EUTROPHICATION

What factors can alter aquatic ecosystems?

Humans! Find food Recreation Waste disposal Cooling of power

plants Transportation Dams, canals

Algae and MicroinvertebratesCan’t be seen with the naked eye

Cyanophyta Chlorophyta Euglenophyta Heterokontophyta

Xanthophyceae Chrysophyceae Bacillariophyceae Phaeophyceae Oomycetes

Rhodophyta Pyrrhophyta

Rotifera Ectoprocta/Bryozoa Arthropoda

Crustacea (superclass) Cladocera (suborder) Copepoda (order)

Chelicerata (subphylum) Arachnida (superclass)

Acari (order)

Phytoplankton Phytoplankton – microscopic plants and some types of

bacteria which obtain their energy via photosynthesis. Important to the ecosystem because

Part of the primary producing community Assist in recycling elements such as carbon and sulfur which

are required elsewhere in the community.

Phytoplankton Basis for aquatic food chain b/c major primary

producers Huge impact on global primary production

Estimated at 105 – 106 g C/year More abundant in well-lighted areas with higher

temperatures Relatively unspecialized physiology, but are

evolved to maintain buoyancy Very little competitive exclusion May be unicellular or multicellular

Phytoplankton Asexual reproduction keep numbers high

Cyanobacteria can double several times/day Diatoms are slower, but can double every 1-2 weeks

Phytoplankton Phylogenetically diverse Important groups:

cyanobacteria dinoflagellates euglenoids green algae diatoms

Diatoms: Order Centrales Characterized by

centric and often circular form

Note also the numerous punctae (pores)

Diatoms

Pleurosira laevis

Nitzschia levidensis

Gyrosigma obtusatum

Dinoflagellates Phylum Pyrrhophyta

“Whirling flagella” Habitat: Mostly

marine, some freshwater

Notes: Unicellular protists 2 dissimilar flagella Many are

photosynthetic

DinoflagellatesNotes:

Heterotrophic dinoflag feed on diatoms or other protists

Marine “blooms” Red tides

Rotifers Phylum Rotifera

“Rotating wheel” Habitat: Fresh water Notes:

Heterotrophic Corona of cilia provide

movement and means to move food toward the mouth.

RotifersNotes:

Sessile, anchors itself with foot

May enter dormancy and form cyst when env. conditions unfavorable

Cysts last up to 50 years

Bryozoa Phylum Ectoprocta

(=Bryozoa) “Moss animals”

Habitat: Marine and both lotic/lentic freshwaters

Notes: Sessile; can be

epiphytic, epilithic or epidendric

Colonial; a number of clones inhabit one structure

Extend ciliated tentacles to filter food from water

Often host a number of smaller organisms

Bryozoa

Cladocera Phylum Arthropoda, Superclass

Crustacea, Suborder Cladocera Water fleas or Daphnia Habitat: widespread; very

important in lentic habitats Notes:

Uses antennae to swim Many populations react to

diurnal cycles, making vertical migrations each day

May be predacious or herbivorous

Head varies considerably from rounded to hooded but eye spot is always distinctive

Body laterally compressed

Cladocera Notes

Parthenogenetic: most eggs are diploid

females (asexual repro)

occasional diploid males fertilize haploid eggs produced by females for sexual reproduction

Copepods Phylum Arthropoda,

Superclass Crustacea, Order Copepoda

Habitat: widespread in marine and fw; may be benthic or pelagic

Notes: may be parasitic,

predacious or detrivorous often seen carrying egg

sacs on both sides develop through several

stages as immature copepods before reaching maturity

Characterized by conspicuous 1st pair of antennae and single anterior eye

Acari (Water Mites) Phylum Arthropoda,

Subphylum Chelicerata, Superclass Arachnida, Order Acari

Habitat: most abundant in lotic waters

Notes: Have 6 legs when

young, 8 when mature Many are parasitic but a

few are predaceous Possess no antennae Related to terrestrial

spiders

Macroinvertebrates Show bioindicators pdf.