AQUATIC BIOMONITORING

BY,APOORVA KULKARNIARJUN R

ARSHIYA SHEHNAZATIYA

AMMAR MEHDI

Introduction

Around the world, freshwater habitats are being subjected to increased level of human disturbance. The effect of disturbance is leading to declination of aquatic species. Hence it is imperative to identify, monitor and conserve aquatic biodiversity. The best way of monitoring pollution in an aquatic environment is by determining changes in the species living there.

Aquatic biomonitoring is the science of studying the ecological condition of rivers, lakes, streams, and wetlands by examining the organisms that live there. Biomonitoring of the impacts of toxicants can be done on a single species or on community.

The organisms which are used in biomonitoring are called as biomonitors. These biomonitors provide the means for regular surveillance and to quantify the amount of pollutant present in the environment. Biomonitoring is based on “when there are changes in water quality, there are changes in fish behaviour”.

Objectives

• To determine the prevalence of organisms with exposures like to cause toxicity.

• To establish reference concentration.

• To assess the effectiveness of attempts to reduce exposure.

• To compare exposure levels in different groups.

• To track trends in exposure over time.

• To set priorities for research.

• To determine which chemicals are taken by living organisms and at what concentration.

Advantages of biomonitoring:

• The indicator organisms acts as a sensitive early warning system which may simulate prophylactic measures to prevent or diminish disastrous effect of pollution.

• Indicator organisms provide a direct method of studying the effects of the prevailing pollution in living organisms and provide a measure of integrated effects of all environmental factors.

• It is possible to study the relationship between concentration of pollutants and its effects when both are measured at same rate.

• Biomonitoring provide possibility of determining species and temporal trends in the occurrence and intensity of effects of several pollutants on natural environment.

• Indicator organisms enable the analysis of polluting compounds by measuring accumulation within indicator organisms.

• Biomonitoring do not depend on electricity for their operation also do not need treatment and are early to indicate the discovering vandalism.

• Biomonitoring can be done in remote areas and no expensive technical equipment is involved.

Organisms and tools used The target organisms are• Bacteria• Algae and aquatic plants• Zooplanktons• Macro- invertebratesSampling devices or tools:Grab or scoop samplers - Devices that are designed to penetrate bottom sediment and collect a sample in standing or flowing water. Nets - Used primarily to collect macro-invertebrate , fish, and zooplankton samples.• Kick net - Useful in small streams with gravelly bottoms and good flow

velocity. • Stream net - Used for fish and macro-invertebrates, depending on net design

and mesh size.• Gill net - Used to sample fish of a certain size range. Useful in large rivers

and lakes.• Seine net - Used to sample fish in shallow ponds or streams. Artificial substrates - Sampling devices made of natural or artificial materials on which organisms colonize.Electroshocking - Used in streams, rivers, and lakes. Strong electrical pulses are sent between two electrodes. Fish will move toward the positive pole.

Nile tilapia E.Coli (bacteria) Algae

Zooplanktons Siphlonurus (Macroinvertebrates)Jellyfish

METALS IN THE AQUATIC ECOSYSTEMS : Metals are present in virtually every area of modern consumerism from

construction materials to cosmetics, medicines to processed foods; fuel sources to agents of destruction; appliances to personal care products. It is very difficult to avoid exposure to any of harmful heavy metals that are so prevalent in our environment. The distribution of heavy metals in manufacturing industries is given below :Table : General Distribution of Heavy metals in Particular Industrial Effluents

Industries Ag As Cd Cr Cu Fe Hg Mn Ni Pb Se Ti Zn

General Industry and Mining X X X X X X

Plating X X X X X X

Paint Products X X X

Fertilizers X X X X X X X X X

Insecticides / Pesticides X X X

Tanning X X

Paper Products X X X X X X X

Photographic X X

Fibers X X

Printing / Dyeing X X

Electronics X X

Cooling Water X

Pipe Corrosion X X

Note : Ag  - Silver; As – Arsenic;Cd – Cadmium;Cr – Chromium; Cu –Copper; Fe –Iron, Hg – Mercury; Mn-Manganese; Ni – Nickel; Pb – Lead; Se – Selenium; Zn-Zinc.

Toxicological aspects• When the pH in water falls, metal solubility increases and the metal particles become more mobile. That is why metals are more toxic in soft waters.• Both localized and dispersed metal pollution cause environmental damage because metals are non-biodegradable.• Metals can become ‘locked up’ in bottom sediments, where they remain for many years.• Bioaccumulation of cadmium in animals is high compared to most of the other metals, as it is assimilated rapidly and excreted slowly.• In fish, the embryonic and larval stages are usually the most sensitive to pollutants. Studies on fish have shown that heavy metals alter the physiological activities and biochemical parameters both in tissues and in blood.

EFFECTS OF HEAVY METALS ON HUMAN HEALTH*The heavy metals hazardous to humans include lead, mercury, cadmium, arsenic, copper, zinc, and chromium. When concentrated in particular areas, they present a serious danger.*Arsenic and cadmium, for instance, can cause cancer. *Mercury can cause mutations and genetic damage.*copper, lead, and mercury can cause brain and bone damage.

For the protection of human health, the maximum permissible concentrations for metals in natural waters that are recommended by the Environmental Protection Agency (EPA), are listed below: Metal

Chemical symbol Concentration in mg/m3

Mercury Hg 0.144

Lead Pb 5

Cadmium Cd 10

Nickel Ni 13.4

Silver Ag 50

Manganese Mn 50

Chromium Cr 50

Iron Fe 300

Barium Ba 1000

EFFECTS OF HEAVY METALS ON AQUATIC ORGANISMSSlightly elevated metal levels in natural waters may cause the following sublethal effects in aquatic organisms: 1.histological or morphological change in tissues2.changes in physiology, such as suppression of growth and development, poor swimming performance 3.changes in circulation4.change in biochemistry, such as enzyme activity and blood chemistry5.change in behaviour; and changes in reproduction

• Toxicity refers to the potential for a substance to produce an adverse or harmful effect on a living organism.

• A toxicant is an agent (e.g., whole effluent discharge) that can produce an adverse Effect( such as abnormal mortality, reproduction or growth) in a biological system, seriously damaging its structure or function or causing death.

• Toxicity tests determine the level of toxicity, if any, present in an effluent and the duration of exposure required for the toxicity to be expressed as adverse effects. Organisms are exposed in test chambers to various concentrations of the effluent. The criteria for effects, such as mortality and reproduction, are evaluated by comparing those organisms exposed to different dilutions of the effluent with those organisms (controls) exposed only to a nontoxic dilution water.

• Acute effects are those that occur rapidly as a result of short-term exposure. Exposure is considered relative to the organism’s life span. The most commonly measured acute effect in aquatic organisms is death.

• Chronic effects occur when an effluent or toxicant produces adverse effects as a result of a repeated or long-term exposure. Chronic effects include lethal and sublethal responses (such as abnormal growth and/or reproduction).

Toxicity tests

• Duration: of 24 or 48 hours.• The test species : Fathead Minnow, or the Mysid Shrimp. Other species may

be utilized to address a specific concern. • These tests are typically static, meaning the organisms are maintained in the

original test solutions for the duration of the test. Procedure:• The effluent sample used in the static tests is collected as a grab or 24-hour

composite . • The sample must be collected and stored with an amount of ice sufficient to

maintain its temperature between 0° and 4°C until receipt at the laboratory. • The effluent samples are prepared for testing by being thoroughly mixed,

allowed to reach standard test temperature, and aerated if dissolved oxygen (DO) is below 4 mg/L. Total residual chlorine is measured.

• The effluent is then diluted with control water, typically to five concentrations (with the appropriate number of replicates) from 0 to 100% effluent. The test vessels are filled with the appropriate volume of test solution.

• Test organisms are transferred to test chambers in a random manner. • Initial DO and pH are measured in separate vessels of dilution and effluent

solutions.

ACUTE TOXICITY TEST

• The test is incubated at 25°C with a 16:8 hour light: dark cycle.

• Mortality of the test organisms is recorded after the defined test period along with final pH, dissolved oxygen, and temperature. An LC50 or concentration of effluent lethal to 50% of the test organisms over the test period is calculated from the mortality data .

• The instream waste concentration (IWC) for the effluent in the receiving stream is calculated (in percent) The LC50 and IWC are compared to predict instream toxicity.

• At test termination, organisms are identified as alive or dead.

• Test results are recorded as “Pass” or “Fail”.

Chronic toxicity test

• The chronic toxicity test measures both survival and reproduction. Including one or more complete life cycles or performing the test during a sensitive life stage allows the detection of subtle adverse effects, such as reduction in growth and reproduction.

• The test solutions are renewed periodically by transferring the test organisms to chambers with freshly prepared solutions. The test is initiated with organisms that are less than 24 hours old and born within 8 hours of each other.

• The original neonate (newly born) introduced into each test container and is monitored for survival as well as for the number of offspring it produces. Exposure of the organisms to differing concentrations of effluent can determine the concentration of effluent expected to cause significant mortality or suppression of reproduction.

• The endpoints of these multiple concentration tests can often be described by the highest concentration that causes no observed effect or the NOEC (No Observed Effect Concentration) and by the lowest concentration that causes an observed effect or the LOEC (Lowest Observed Effect Concentration).

• The geometric mean of these concentrations, termed the chronic value, represents an estimation of the effluent concentration at which observed effects begin to appear.

• The study was carried out in Nakivubo wetland at inner Murchison bay on Lake Victoria, Kampala city, Uganda.

• The Nakivubo River and its tributaries provide the main drainage channel for Kampala, carrying wastewater mainly from the industrial area and from residential areas to the north-west of the city.

• The aim of this study was to actively biomonitor selected trace heavy metals using Nile tilapia (Oreochromis niloticus) (The dissolved oxygen (DO) limit for Nile tilapia is 0.01 mg/l).

• Six sites (1, 2, 3, 4, 5, and 6) were chosen for active biomonitoring and physico-chemical investigation of water pollution.

• Nile tilapia was set in cages in Murchison bay for six weeks, and sampling was done every 2 weeks for active biomonitoring and weekly for physico-chemical variables. Fish tissue was dissected and gills, liver and muscle removed for heavy metal analysis.

• A Shimadzu AA 6401F Atomic Absorption Spectrophotometer (AAS) was used to determine the levels of copper, manganese, zinc and chromium in these tissues.

THE CASE OF NAKIVUBO WETLAND ALONG LAKE VICTORIA.

• Nile tilapia fish (Oreochromis niloticus), 60- 100 g were obtained from the fish farm of Aquaculture Research and Development Centre (ARDC, Uganda) and put in ‘hapas’ (cages) at selected sampling sites. The sample size was 40 fish for each.

• During sampling, four fish and water samples were taken from each site and transported to the biochemistry laboratory at Makerere University.

• Each fish was weighed, total and standard length measured before dissection.

• The fish that did not survive field exposure were thrown away.• Dissection was carried out on an aluminum foil work place using

stainless steel tools and wearing surgical gloves. Muscle, gills and liver were removed for metal analysis.

• After dissection, the tissue samples were wrapped in aluminum foil and frozen at -80 0C prior to metal analysis.

Sampling protocols

• The Food and Agricultural Organization (FAO) method involving the digestion of the sample in an open beaker on a hot plate was used.

• FAO method involves 10g fresh weight in 15ml of freshly prepared 1:1 (v/v) nitric acid- hydrogen peroxide, using this the varied weight of the pooled samples up to 2 g were calculated backwards to coincide with this method.

• The beakers were covered with a watch glass and set aside for about 15minutes in order to allow the initial reaction to subside. The beaker and its contents were heated at a temperature not exceeding 160 0C. Boiling was done for 30min and subsequently reducing the volume.

• The contents of the beaker are transferred to a 25ml volumetric flask and diluted to the mark with deionized water for analysis.

• Stock standard solutions prepared for all the four metals.• Required volumes of standard solutions for each metal used to set up a

standard linear graph is used to determine the concentration of metal in samples of gill, liver and muscle from each site. Average concentrations were then calculated and converted from mg/l to μg/mg.

Sampling analysis

• The pH range and temperature for all the seven sites was within permissible effluent standards for Uganda 6-8 and 20-35 0C respectively.

• Site 5 had the highest number of fish kills (77.5%), followed by site 6 (60%) and site 4 (55%).100% of the fish stocked in site 7 survived.

• Results from analysis showes mean amount of all the tested metals in fish was greater than that in water.

• Comparison of heavy metals basing on tissue type and period only, showed that copper had the highest bioaccumulation as compared to other heavy metals in all Tissue.

• Bioaccumulation although on average chromium recorded the lowest levels in Oreochromis niloticus as compared to other heavy metals.

• The high levels of copper in the liver can be ascribed to the binding of copper to metallothioneins (MT), which serves as a detoxification mechanisms.

• The accumulation of copper reduced after a period of six weeks which could imply that the liver is able to eliminate copper.

Results

• The low levels of dissolved oxygen in sites 3, 4 and 5 could have been due to the high organic load from the wetland which requires oxygen for decomposition of algae.

• Site 7 had NH4-N levels higher than sites 1 and 2 which could be due to decay of grass.

• Losses of fish in Sites 5 and 6 could have been due to clogging of the cages by water hyacinth and thus not allowing entry of for improving DO levels and provision of food.

• In general, bioaccumulation of metals in tissue was recorded highest in the order gills>muscle>liver after a period of 6 weeks. This is because gills are the main route for metal penetration from the water.

Graphs showing variations in concentration of metals in sampling period in liver and muscle with respect to sites

Disadvantages of biomonitoring:

• Biomonitoring is not useful for assessing exposure to substances that exhibit toxic effects at the site of first contact where these substances are poorly absorbed.

• Biomonitoring is only useful when the relationship between waterborne levels, internal dose and adverse effects is known for specific chemicals.

• A major limitation is the lack of detailed information on the fate of industrial chemicals in humans.

• Most of the toxicokinetic data available are for experimental animal studies and most be extrapolated to humans.

• When indicator organisms are spread out over a wide geographical area it posses a problem.

Discussion

Various anthropogenic activities are the cause for disturbance and sometimes declination of aquatic species thereby stressing the need to take up biomonitoring as the next trend to conserve water quality as well as aquatic life though the plight of organisms used for the toxicity test may be a cause of moral concern , logical reasoning otherwise sheds light that a fewer organisms are being sacrificed instead of a whole species being at risk of extinction .

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