Freshwater ecosystems

Ideal indicator

1. Taxonomically sound & easy to identify

2. Widespread distribution

3. Numerically abundant

4. Large body size

5. Ecological requirements known (autecology)

6. Narrow ecological demands

What are biological indicators

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

1. The state of the environment

2. Change from ‘normal conditions’

3. Highlight the pressure causing a change

What are the types of indicators?

1. Sentinel organisms

2. Community level indicators

3. Organism level indicators

• Biochemical indicators

• Life history responses

• Morphological deformities

MACROINVERTEBRATE are a key indicator group

Advantages of Macroinvertebrates in Water Quality Assessment

1. Wide diversity (species & functional groups) and abundance

2. Relatively sedentary → occurrence of most can be related to conditions at place of capture

3. Life cycle of 6 months or longer → provides overview of prevailing physical/chemical conditions

4. Sampling relatively easy and cheap

5. They respond to environmental stress → integrate the effects of short-term perturbations.

Disadvantage of using Macroinvertebrates in Water Quality Assessment

1. Biological expertise needed to identify some groups.

2. Autecology of various groups needed as absences may be related to habitat or life cycle factors

Macro’s respond to environmental stress

1. Oxygen depletion

2. Direct toxicity

3. Loss of microhabitat

4. Siltation of habitat

5. Food availability changes

6. Competition from other species

Bioassessment using Macroinvertebrates

Analyses Measures (Metrics)

Evaluate and express the presence/level of impact

Univariate approach 5 possible categories:

1. Taxon Richness

2. Composition Measures

3. Community diversity & Similarity indices

4. Functional Feeding Group and other species trait

5. Biotic Indices

Taxon richness

Measure of the no. of different taxa (group of one or more populations of an organism(s)) present in a community or sample

Community diversity & Similarity indices

Quantitative measure used to determine the degree of resemblance between two or more samples, sets or structures. Often expressed as a percentage or a value between 0 and 1

Functional feeding group

Classification system for organisms (macros especially), based on their primary method of acquiring food rather than their taxonomic group.

Biotic indices

Incorporate info on pollution tolerance/biological tolerance to provide overall measure of water quality (numerical value).

Biotic Index Systems for Macroinvertebrates

1. Ireland → EPA Q-Value score

2. UK → BMWP score (Biological monitoring working party) ASPT

Q-values

Assigned depending on mix of pollution-sensitive vs pollution tolerant

Macro families can be divided into 5 pollution sensitive groups

A. (Highly sensitive),; E (tolerant)

Proportions of the various groups present in the river indicates the prevailing water quality, yields Q-values score from 1 to 5

Sensitive groups A to C

Tolerant Forms (D & E)

What are the threats to freshwater & their biodiversity?

1. Pollution

• Types and extent increasing

• Over 1500 contaminants have been found in freshwaters

• Top gun: Nutrients, Organic waste, Sediment, Pesticides

2. Habitat degradation

• Flow modification (dams)

3. Surface waters have also been drained, straightened, over-abstracted, fragmented

4. Global wetlands are vanishing three times faster than forests

5. Overexploitation for water

6. Overexploitation for organisms (target and bycatch)

7. Invasive species

8. New emerging threats (climate change)

What are the statistics from the reports on water quality within Ireland?

Types of water bodies

Types of Rivers

Ponds provide many benefits

• Stepping points for biodiversity in highly modified landscapes

• Ponds often support greater diversity than other freshwater habitats (lakes/rivers), sustaining many rare and endangered aquatic taxa and act as important refuge in heavily modified landscape.

• Contribute to regional biodiversity

• Carbon sequestration

• Water retention

• Amenity & education values

Riparian vegetation provides vital benefits for water quality protection and biodiversity, why?

Important two-way subsidies

1. Leaf litter fuels aquatic food webs, insects from riparian vegetation are an important diet of salmonids

2. Emerged adult aquatic insects contribute to terrestrial predator diets (bats, birds and spiders).

3. Riparian vegetation can attenuate diffuse population and regulate extremes in temperature (climate change pressure)

Degraded or no riparian buffer zones in many catchments in Ireland leave surface waters open receptors for diffuse pollution.

Macroinvertebrates importance (again)

Multiple functions in freshwater from processing leaf litter and detritus, and as prey for fish, other invertebrates, birds and mammals. Also helps maintain clean clear water.

EPT (Ephemeroptera, Plecoptera, Trichoptera)

Pearl mussel (special invertebrate) flagship species

• Lives up to 120 years in Ireland

• Depends on salmonids complete their life cycle

• Requires the highest water and habitat quality

• Protected under the Habitats Directive

Due to land-use pressures (e.g. drainage, nutrients and fine sediment inputs) pearl mussels are threatened with extinction.

Freshwater anthropogenic problems

• Run-off of nutrients, excess sediment and pesticides from agricultural lands and farmyards.

• Land drainage, navigational dredging and the presence of barriers such as dams, weirs or culverts in water courses.

• Poorly treated sewage from urban wastewater treatment plants, domestic treatment systems and storm water overflows.

• Run-off of nutrients and excess sediment from forestry operations

Ireland’s freshwaters are receiving and are being impacted by ‘cocktails’ of multiple stressors (pollutants) delivered along varying pathways often from several sources, requiring the targeting of the right measures in the right place.

The significant pressures impacting Ireland’s freshwaters goes to-

Agriculture is the dominant source of pressure on freshwaters following by hydro-morphology and urban wastewater.

Eutrophication

The biological effects of an increase in the concentrations of nutrient

Caused by the availability of nitrogen and phosphorus, commonly present in soil and water in the form of nitrate and phosphate.

It leads to slight to moderate pollution and failure to meet the goals of the WFD

General characteristics of Oligotrophic vs Eutrophic waters

The amount of P required by living organisms is small but it is the most common growth-limiting factor in freshwaters

• Little bio-available P released from breakdown of rocks (common component of rocks up to 7%)

• Root zone in soils retain much P

• Rainwater contains little P

• P reaching freshwaters is readily absorbed onto particles → become unavailable

Organisms require small amounts and can store many times their immediate needs

Anthropogenic sources of Phosphorus

1. Run-off agricultural lands

2. Forest fertilisation

3. Tree felling (brash)

4. Inadequate sewage treatment

5. Use of detergents and other household P-containing products

6. Urban areas

7. Rural dwelling septic tanks

8. Leachate from dumps

Water Frame Directive standards

Symptoms of Eutrophication in lakes

1. Excessive algal blooms; low water quality (pea soup)

2. Increased turbidity, reducing amount of light and oxygen reaching submerged plants → loss of habitat for some invertebrates and fish

3. Diversity of aquatic plants tend to decrease

4. Macroinvertebrate communities dominated by tolerant species.

5. Possibility of toxic blue green algae (HABS produce toxins)

6. Oxygen depletion in deep water as organisms decomposing the increased biomass consume O

7. P recycled from sediments

8. Increased water treatment costs

9. Water may be unacceptable to taste or odour due to the secretion of organic compounds by microbes.

10. DOC secreted by algae may increase cost of chlorination and also produce chlorinated phenolic substance.

Algae adapted to low P

• Luxury consumption/uptake more P than is necessary to support their next cell cycle

• Storage as polyphosphate granules

• Production of enzyme alkaline phosphate (ALP - cells and to exterior environment)

Harmful Algal Blooms (HABs)

Component of HABs (Dinoflagellates, diatoms and cyanobacteria)

Symptoms of Eutrophication in Rivers

1. Excess macrophytes & especially filamentous algae Cladophora sp. and marginal vegetation of rivers

2. Strong diurnal fluctuation in dissolved oxygen levels (night time deficits)

3. Fish kills in warm weather or salmonid populations move out

4. Pollution-sensitive macroinvertebrates disappear

5. Stress leading to fish kills

Remediation/Mitigation measures

1. Subsiding of sewage treatment plants

2. Nutrient management on farms; only apply what is needed, soil testing

3. Diverting wastewater to treatment plant or constructed wetland

4. Maintaining vegetated buffer zones along watercourses

5. Slow the flow (uptake further upstream)

6. Reducing livestock

7. Reduce soil compaction

8. Undertake conservation/contour tillage

9. P reduction may not be sufficient in hypertrophic lakes (accumulation of nutrients for many years)

Main forms of Nitrogen in Freshwaters

1. Ammonia

2. Nitrite

3. Nit

Nitrogen cycle in Freshwater ecosystems

1. Thick black lines indicate main pathways in terms of mass transfer.

2. Dotted lines are those involved in recycling and mineralisation in the water column.

3. Nitrogen is mostly available as nitrate, which passes from rain to rivers and lakes, where much of it is take up by algae and used for growth, then deposited in the sediments.

4. Nitrogen in algae is eaten by zooplankton (lakes) and insect larvae (lake benthos and streams) is excreted as ammonia which is recycled back to algae in the summer.

5. Note the two anoxic sections of the cycle (N2 fixation and denitrification), which involves blue--green algae and bacteria; in contrast to the rest of the cycle that occurs under oxygenated conditions.

6. Most N2 fixation occurs in the plankton, whereas denitrification occurs in sediments especially in estuaries and wetlands. Most organic nitrogen in aquatic ecosystems is present as plant or animal nitrogen and organic detritus (particulate or DON = dissolved organic nitrogen).

Ammonia WFD standard

Unoionised Ammonia is Toxic to fish in high concentrations

Acute exposure causes:

• Increase in gill ventilation

• Hyper-excitability

• Convulsions

• Death

Chronic exposure to unionised ammonia

1. Affects

2. Causes decrease in reproductive capacity (egg viability, date of spawning etc)

3. Causes decrease in growth (condition factor drops)

4. Increases susceptibility to disease

5. Get progressive deterioration in physiological functions

Nitrite NO2

• Toxic to fish in small conc.

• Causes hyperventilation & impacts cardiovascular function

Main toxic action of nitrite on aquatic animals:

1. The conversion of oxygen-carrying pigments into forms that can no longer transport oxygen leads to severe hypoxia and can ultimately cause death.#

2. In fish, entry of nitrite into the red blood cells is associate with the oxidation of the iron, converting haemoglobin into methaemoglobin that is unable to release oxygen to body tissues because of its high dissociation constant

3. Get a similar oxidation reaction with copper in the hemocyanin of crustaceans as it is converted into methemocyanin

Nitrite thresholds

Nitrate NO3

Main toxic action of nitrate on aquatic animals is due to the conversion of oxygen-carrying pigments (e.g. hemoglobin, hemocyanin) forms that are incapable of carrying oxygen (e.g. methemoglobin)

1. Not usually toxic to fish (low permeability of gills to nitrate)

2. Can promote eutrophication

3. Has implications for quality of drinking water

Nitrate toxicity to fish

1. Potential for toxicity increases with increasing concentration and exposure time

2. Egg and dry appear to be most vulnerable

3. Cation composition (protected by hardness) of water may affect toxicity e.g. freshwater fish are more susceptible

Morphological problems in Irish Rivers

Invasive alien species

Plants, animals, pathogens etc are non-native to an ecosystem and which may cause economic or environmental harm or adversely affect human health.

Invasive species: Quagga mussel

1. Filter feeding bivalve

2. Similar to zebra mussel

3. Biofouling

4. High densities

Graph of invasive species

Stary stonewort (Nitellopsis obtusa)

1. Native to Europe but invasive in UK & Ireland

2. Recently expanding

3. Significant monocultures e.g. 84ha

4. 250ha in 3 bays in L. Ree

Acid mine drainage

1. Low pH

2. Toxic heavy metal concentrations

e.g. Lead and Zinc

Impacts from Forestry Operations

• 10.5% forest cover (3/4 coniferous)

• Takes 35-40 years to reach maturity

• Most planted on upland peaty soils

WFD characterisation

Forest operations are potential source of diffuse pollution:

• Acidification

• Eutrophication

• Siltation

Tree harvesting

Literature indicates felling increases sediment and nutrient losses in streams draining the catchment

Sensitivity of Freshwaters

Aluminium

Measurements

• Total aluminium

• Inorganic aluminium - potentially toxic to fish and other biota

Continuum of Change

Community of macroinvertebrates change in response to changes in food supply and abiotic factors

Weaknesses of RCC (River-continuum concept) 1

1. Works best for temperate rivers with season inputs of organic matter

2. Relates to the main channel, omitting side channels, marshes, backwaters and floodplains and other linkages.

3. Does not take into account as ‘‘discontinuities’’ such as lakes or dams

4. Does not take into account various types of rivers sources

Weaknesses of RCC (River-continuum concept) 2

1. High biological diversity in mid-reaches (2nd/3rd order) due to greatest diversity of substrate, flow and food sources (unlikely that all coincide

2. High diversity of mid reaches due to downstream drift of insects and upstream movement of crustaceans (true for large rivers confined to their channels but not for large floodplain rivers, which accumulate substantial input of energy from the floodplain.