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Aquatic Ecology

Aquatic Ecology. How much water is there on Earth?. Habitats and Communities. Marine systems: three major zones Off shore or open sea Neritic or near shore Intertidal – alternately submerged and exposed Few insects some of great interest – discuss later. Devoid of insects.

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Aquatic Ecology

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  1. Aquatic Ecology

  2. How much water is there on Earth?

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

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

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

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

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

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

  9. 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

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

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

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

  13. 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

  14. 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

  15. Lake Zonation

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

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

  18. 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

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

  20. Lake Communities Plankton: • Insects poorly represented • Chaoboridae only planktonic insect

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

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

  23. 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

  24. 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)

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

  26. 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

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

  28. Lake Communities Chaoborus: • Oxygen = entraining agent • High 02 1% migrated • Low 02 30% migrated

  29. 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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  31. Lake Communities Chironomidae: • 1st 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

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

  33. 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

  34. 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

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

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

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

  38. 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

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

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

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

  42. 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

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

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

  45. Lake Communities Benthos: • Hutchinson - insect fauna of lakes fall into three depth categories • All other orders with exception of Diptera • Amphibiotic (aquatic larva, terrestrial adult) • Extract O2 from water • Restricted to relatively shallow water

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

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

  48. Exam topics

  49. Hoeinghaus et al. 2007 • 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?

  50. 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

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