L5 Detecting impacts using biological indicators invertebrate adaptions

Quiz on lecture 4 topics

Macroinvertebrates are key indicator group

Chemical assessment of pollution demands intensive sampling:

• to detect inputs, but also

• to detect the extreme conditions which affect fish and other aquatic life

• Now in a supporting role

Biological indicators

Organism(s) or attributes of the community which can be used to provide information on:

• State of the environment

• Change from ‘normal conditions’

• Highlight the pressure causing a change

Advantages of macroinvertebrates in water quality assessment

• Wide diversity and abundance

• Relatively sedentary - occurrence of most can be related to conditions at place of capture.

• Life cycle of 6 months or longer - provides overview of prevailing physical/chemical conditions

• Sampling relatively easy and cheap; no ethics approval required

• They respond to environmental stress

Disadvantages of macroinvertebrates in water quality assessment

• Biological expertise needed to identify some groups

• Knowledge of various groups needed as absences may be related to habitat or life cycle factors (e.g. seasonal emergence).

Mayfly nymph - Family Heptageniidae

Pollution-sensitive

Chironomids are highly versatile species that can tolerate a very wide range of environmental stresses

Chironomid larvae (non-biting midges) - pollution tolerant

Type of fly

Chironomus sp. (bloodworm)

Tolerates low oxygen conditions associated with organic pollution

Macroinvertebrate communities found in:

Clean water → moderate pollution → heavily polluted water

Clean waters = support good variety and numbers of pollution-sensitive macroinvertebrate taxa PLUS some pollution-tolerant taxa

Polluted water = dominated by pollution-tolerant macroinvertebrate taxa

Different types of Invertebrates

A large variety of invertebrates indicates a generally healthy stream with diverse habitats.

Different types of stoneflies, mayflies and caddisflies

As a whole, these groups of insects are sensitive to pollution, metals, low oxygen and warm water.

If a variety of stoneflies, mayflies and caddisflies are found, usually indicates that the stream is generally healthy and has diverse habitats.

Intolerant or sensitive invertebrates

Some animals are especially sensitive and will be the first to disappear if there is some type of disturbance.

If intolerant or sensitive invertebrates are present, it usually indicates the stream is generally healthy and has diverse habitats

Predators

Predators are top of the food chain

If they are present, the stream has diverse habitats that support a variety of prey animals

Clingers

Clingers attach themselves on and under cobbles and gravel where they feed.

When cobbles become clogged by sand and silt, these animals will not survive.

If clingers are not present, there may be too much sediment in the stream from erosion.

Long-lived invertebrates

Long-lived invertebrates require more than a year to complete their life cycles and if they are absent from a stream, it may indicate some type of disturbance.

Example, if the stream dries out at some point during the year, these animals may not survive.

Tolerant invertebrates

Some invertebrates tolerate poor conditions such as polluted water, warm temperatures or degraded habitats.

As a stream becomes more disturbed, the number of tolerant invertebrates increases.

Dominant invertebrates

As stream health declines, a few groups will dominant the overall invertebrate numbers.

Water framework directive

Legal framework for the protection and management of water resources throughout the EU

Main objective:

• To protect and maintain high and good status of all waters (where such status already exists) by 2015 and by 2027 latest

• Prevent any deterioration in existing status of waters

• Restore all waters that are impaired so that they achieve at least good status by 2015 and 2027 at latest

Why monitor?

• The WFD calls for the protection and restoration of clean water across Europe

• A key step in this process is for Member states to assess the health of their surface-waters through national monitoring programmes.

WFD Status Ratings

Principles for classification of high, good and moderate ecological status of a water body, based on anthropogenic alterations using Ecological Quality Ratios (EQR)

EPA Q-Values: Q1 to Q5

Q-value assigned depending on mix of pollution-sensitive vs pollution-tolerant

Fish as indicators

Advantages:

• Good long-term (years) integrators

• May include variety of species which cover several trophic levels - provide insight into potential impacts at multiple levels in food web

Disadvantages:

• move - short and long distance movements

• Life cycle can be complex

Fish assemblage structure reflects integrated environmental health

• Environmental requirements for fish relatively well known

• Top of the food chain - important to avoid contamination of human food chain

Difference between fish and invertebrate assessment methods

• Fish sampling requires large spatial scale

• Fish methods must apply to wide range of river/lake sizes

• Fishes and invertebrates not necessarily equally sensitive to same stressors

Fish - WFD requirements

• Species composition

• Abundance

• Age structure

• Fish released alive where possible

• Sub sample removed for lab analysis

Rivers

Population estimation for salmon: Depletion method

Stretch of river 10 - 15x stream width

Stream section sampled repeatedly; fish captured are removed

→ each sampling pass should remove fewer fish

→ Total population can be estimated by extrapolating the decreasing number to 0

Lakes

• Electofishing in shallow systems

• Gill netting

• Mark-recapture (recapture min 10% of marked fish)

Key measurements

• Species (stocked or wild)?

• Length

• Weight

• Condition/evidence of disease

• Scales for ageing

Ageing fish

• Calcified structures, such as scales and bones used to determine age of fish

• Scales are most widely used because they are easy to collect and store

• Fish scales and bones grow bigger as the fish gets older, with new layers of growth deposited around the scale each year

• Circuli - growth rings - gaps between them can be measured under magnification to determine growth rate.

• Some fish species - scales difficult to age - otoliths (bones from inner ear) used instead

Otolith with rings for aging

Important to distinguish natural variation from anthropogenic impact

Natural factors affecting distribution & community structure aquatic biota:

• water chemistry

• sources of organic matter - continuum concept

• physical habitat

Adaptions to life in flowing water

Two key physical forces affecting aquatic biota:

• Flow

• Substrate (these are interlinked)

Biota adapt to avoid being swept downstream

Adaptions:

• attachment structures

• modified shape

• behaviour

Attached mosses & macrophytes

Attachment mechanisms of macroinvertebrates and other aquatic biota

Flattened mayflies (Ephemeroptera)

Family Heptageniidae, Genus Rhithrogena

Flat, teardrop-shaped body - well suited to clinging to rocks in fast water where they feed on detritus and algae.

Attached & streamlined

Freshwater limpet - streamlined flattened conical shape of shell helps animal cling on in fast currents

Clingers

Riffle beetles have large claws on the feet for holding on

Caddisfly larvae have hooks at the end of the abdomen

Streamlining

Body width needs to occupy less than 36% of the total body length

Mayflies (Ephemeroptera) and stoneflies (Plecoptera) living in turbulent water have long tails that act as fins to assist in streamlining and recovery if they become dislodged

Suction

Leeches (sub-class Hirundinea) have 2 suckers, one on each end rear sucker used primarily for locomotion and to latch onto host when feeding

Black fly larvae (Simuliidae) have a suction pad that attaches them to the substrate.

If they are dislodged, they can spin out a safety line which catches the bottom - they then use their proleg to crawl back along it.

Burrowing

Midge larva (Diptera: Chironomidae) in its U-shaped burrow

Oligochaete worms (Oligochaeta: Tubificinae) feeding head-down in sediments

Surface Dwellers

Pond skaters use surface tension to walk on water

Fine hairs on the insect’s feet repel the water

The ends of its thin legs are angled sideways so they do not break through the film on the water’s surface

Whirligig beetles skate on the water surface because of their oar-liked hind legs

They can beat their hind legs 60 times per second, which propels them over the surface.