Aquatic Ecology

How much water is there on Earth?

Habitats and Communities Marine systems: three major zones 1.Off shore or open sea 2.Neritic or near shore 3.Intertidal – alternately submerged and exposed Few insects some of great interest – discuss later Devoid of insects

Habitats and Communities Estuaries: brackish water Ecotone between inland water and the sea Richer aquatic insect fauna than marine

Habitats and Communities Lotic: inland running water 1.Crenal – spring fed headwaters 2.Rhithral – streams and small rivers 3.Potamal – large rivers Highest diversity of aquatic insects

Habitats and Communities Lentic: inland standing water 1.Lacustrine – lakes and ponds 2.Palustrine – marshes and swamps –Shallow habitats –Ecotones between aquatic and terrestrial Greatest insect diversity associated with vegetation

Habitats and Communities Subterranean waters: Hypogean 1.Troglal – caves 2.Stygal – groundwater Relatively sparse insect communities except were merging with surface waters

Habitats and Communities Biotic Community: Comprises all populations in a given habitat -- including everything from bacteria to vertebrates and higher plants

Habitats and Communities “Planktonic Community” Plankton – organisms that remain suspended Adaptations for vertical migration and/or to remain at certain depths Few insects adapted to planktonic existence

Habitats and Communities “Nektonic Community” Nekton – Strong swimmers not at the mercy of the currents. Few insect representatives

Habitats and Communities “Pleustonic Community” Pleuston – Organisms at air-water interface Atmospheric breathers that require aqueous medium for other needs

Habitats and Communities “Benthic Community” Benthos – organisms associated with substratum Bottom materials, plant beds, logs or other solid surfaces

Lentic Freshwaters Lakes provide diverse habitats for aquatic insects Environmental conditions –Distinct spatial gradients –Temporal changes pronounced Aquatic insect communities change w/ gradients in lakes and between lake types

Lake Zonation Limnetic Zone – open water devoid of rooted vegetation Littoral Zone – shallow marginal areas characterized by rooted vegetation Sublittoral Zone – transition between well- illuminated upper strata and Profundal Zone Profundal Zone – light insufficient for photosynthesis

Lake Zonation

Lake Communities Pleuston: organisms associated with surface film Epipleuston – upper surface –Water striders Hypopleuston – lower surface Meropleuston – not continuous resident –Mosquito larvae

Lake Communities Pleuston: Adaptations for surface residence –Small size –Furcula Collembola –Hydrophobic cuticle Gyrinids have hydrophobic dorsum and wettable venter

Lake Communities Pleuston: Three families of Hemiptera = striders –Hydrometridae – elongate body and legs Water measurer –Gerridae and Veliidae Supported by full length of tarsi Tarsi covered with “hairpiles” Secrete substance that lowers surface tension

Lake Communities Pleuston: Diptera limited to mosquitoes Hydrophilid beetles “walk” inverted on underside of water surface

Lake Communities Plankton: Insects poorly represented Chaoboridae only planktonic insect

Lake Communities Chaoboridae: World wide –Lakes and ponds Nearly transparent Prehensile antennae Feed on zooplankton and mosquitoes

Lake Communities Chaoborus: Tracheal system reduced to kidney shaped air sacs –One pair thoracic; another in abdomen Use these “hydrostatic organs” to adjust buoyancy

Lake Communities Chaoborus: 2 types of vertical migration –Full – generally in lake species Reside in bottom mud during day Feed in water column at night –Reduced – predominately in pond species = Remain in epilimnion

Lake Communities Chaoborus: Limited migration of some species may explain why they are missing from lakes with fish (C. americanus) Others coexist with fishes (full), and are found in fishless lakes (reduced; C. flavicans)

Lake Communities Chaoborus: Different larval instars exhibit different migratory behavior C. trivittatus –1 st and 2 nd instars restricted to surface water –3 rd and 4 th move to deeper water during day –Smallest at surface, size  with depth

Lake Communities Chaoborus: –Regular depth distribution of size classes apparently related to food size distribution and predation Larger items generally deeper Greater vulnerability to visual predation

Lake Communities Chaoborus: Light = entraining agent –Benthic & planktonic phases can be artificially reversed in lab –instars react differently

Lake Communities Chaoborus: Oxygen = entraining agent –High 0 2 1% migrated –Low % migrated

Lake Communities Chaoborus: Horizontal migration –Spring migration of larvae to littoral zone –Adaptation enabling exposure to warm water prior to pupation

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Lake Communities Chironomidae: 1 st instar adapted to planktonic existence for dispersal –Larvae positively phototactic 1-3 days –Vertical migrations common w/ diel light –As larvae mature shift from photophilous to photophobic

Lake Communities Chironomidae: Late instars may again enter plankton 1.Move to well-aerated water 2.In some species, late instar individuals follow pattern described for 1 st instars

Lake Communities Ranatra montezuma: Hemipteran Nocturnal planktonic behavior As light drops below 100 lux, move from littoral to limnetic zone Feed on Hyalella montezuma, return to littoral zone during day

Lake Communities Nekton: Nekton distinguished from plankton by directional mobility; from benthos by association with open water Although many aquatic insects swim, they are associated with hard substrate

Lake Communities Nekton: Truly nektonic species restricted to a few hemipterans and coleopterans Hemiptera nektonic species include Notonectidae, Corixidae and Belostomatidae

Lake Communities Nekton: Anisops and Buenoa (Notonectidae) use hemoglobin to control buoyancy Prey on small arthropods in open water column

Lake Communities Nekton: Relationship between habitat and leg structure –Buenoa – open water –Hind legs for rapid pursuit –Forelegs and midlegs for prey capture

Lake Communities Nekton: Relationship between habitat and leg structure –Notonecta – underside of surface film Feed on moving prey as well as those caught in surface film Leg structure is intermediate

Lake Communities Nekton: Corixidae +Elongate, flattened, hair-fringed hindlegs +Most restricted to water < 1 m Planktivorous spp. are nektonic

Lake Communities Nekton: Belostomatidae –Most are sit and wait predators –Lethocerus = nekton Coleoptera –Only largest Dytiscidae and Hydrophilidae

Lake Communities Benthos: Majority of insects in lentic habitats are benthic Collectively, aquatic insects make up to 90% of total benthic fauna

Lake Communities Benthos: Several orders have highest diversity and abundance in lentic habitats –Odonata (dragonflies) –Hemiptera –Coleoptera –Diptera (some families exclusively lentic) –Hymenoptera –Lepidoptera –Neuroptera

Lake Communities Benthos: The composition and relative abundance of aquatic insects is integrated along depth profiles

Lake Communities Benthos: Hutchinson - insect fauna of lakes fall into three depth categories 1.Aquatic adults that never developed gills –Hemipterans and coleopterans –Rarely occur in water depth more than 3 m –Most surface for air

Lake Communities Benthos: Hutchinson - insect fauna of lakes fall into three depth categories 2.All other orders with exception of Diptera Amphibiotic (aquatic larva, terrestrial adult) Extract O 2 from water Restricted to relatively shallow water

Lake Communities Benthos: Hutchinson - insect fauna of lakes fall into three depth categories 3.Only certain dipterans have colonized profundal zone –Amphibiotic –Chaoboridae –Chironomidae

Lake Communities Taxonomic richness of benthic insect communities declines with depth Max richness at depths of 1-2 m

Exam topics

Hoeinghaus et al Which river concept explains energy sources in 10 tribs of Parana’ river? Low-gradient, high gradient, reservoirs C,N isotopes for fishes, molluscs, plants, detritus Big conclusions? –Lowland river foodwebs = C from aquatic macrophytes –Reservoirs = C from algae more important –High gradient rivers = C from filamentous algae Relate to river concept?

Lytle and Poff 2004 Adaptations to survive floods and droughts ID adaptations Modes: know examples Timing of flow = life history adaptations Predictability = behavioral adaptations Magnitude/freq = morphological adaptations Human impacts

Stone et al Macroinvertebrates of ag streams What variables impact them? Methods? Sites? Sampling? What attributes were compared? Which attributes varied with physical variables? What impacts caused low scores for macroinvertebrates?

Merritt and Cummings Chapter 3 Sampling Devices Sorting, preservation Taxonomic resolution

Merritt and Cummings Chapter 5 Habitat, life history Marine paradox Hydraulics Habitats Upstream movements