Journal of Aquatic Ecosystem Health

Although the identification of organisms to the levelof species is the ideal in studies of marinemacrobenthos, there are situations where such a finelevel of taxonomic discrimination may be eitherimpossible or unwarranted, for example when much thefauna is undescribed, or if the task for which samplesare collected does not require them to be identifiedto the species level. The idea that abundances ofhigher taxa, or particular groups of organisms, may beused as surrogates for the total fauna in such studiesis explored in this paper using data from theNorwegian sector of the North Sea. The generalconclusion is that, in surveys of soft sedimentmacrofauna in disturbed areas of the North Sea wherepollution imposes simple spatial gradients on thebenthic communities, little information aboutinter-sample relationships is lost using data based onfamily, polychaete species, or polychaete familyabundances, rather than species abundances. In morepristine areas where spatial patterns are determinedby a number of processes, correlations betweencalculated diversity indices and similarity in faunalpatterns between species and family abundances arestill very high, but less so for polychaete species orpolychaete family abundances. This suggests thatidentification to the level of family may besatisfactory in many routine monitoring surveys,andidentification of only the polychaetes, either to thelevel of species or family, may also be a possiblealternative if there are clear disturbance gradientsin the survey area. Polychaetes are of importance indisturbed areas because the group contains tolerantand intolerant species, and in undisturbed areasbecause within the taxon species have a greater rangeof trophic and reproductive strategies than withinother taxa. Ultimately it is the distribution ofspecies, their identities, and their interactions witheach other and with the environment, that are ofinterest. The use of surrogates is likely to be mostadvantageous if it is only the extent of pollutioneffects from a discrete source that matters, andspecies level baseline studies have already beencompleted.

The mining for mineral resources and the disposal of wastematerials are the major potential sources of environmental hazard for the deep-seasystem. Polymetallic nodules, manganese crusts, metalliferous sulphidic muds and massiveconsolidated sulphides might serve as exploitable sources of various metals, whilstphosporite deposits represent a further resource. The main types of waste targeted for deep-seadisposal are munitions, radioactive wastes, large offshore structures, sewage sludge anddredge spoils. Furthermore, it has recently been proposed to introduce hugequantities of carbon dioxide from industrial processes into the deep ocean in order tomitigate the greenhouse effect. A description of the different mineral resources and wastematerials is given, including information on the related technology and the status of thedumping and mining operations, respectively. The predicted effects of waste disposaland mining on the deep-seaenvironment are reviewed, possible impacts including removalof settling benthic substrate and mechanical stress exerted on soft bottomcommunities, plus impacts of sediment plumes, toxic materials and degradable organic matter.An overview of the major environmental studies in the deep sea is given. Twocategories of study can be discerned, research conducted after environmental impacts (e.g.,the monitoring of contamination by sewage sludge disposal off the New York Bight)and precautionary environmental studies on potential impacts threatening the deepsea environment in connection with its future human use (i.e., studies aiming toassess the possible effects of deep-sea mining). The development of large scale in-situexperiments was a new approach to the environmental risk assessment of nodule mining inthe deep sea. In the course of the DISCOL project in the south-east Pacific, the firstexperiment of this kind was implemented and monitored for three years. Another type oflarge-scale in-situexperimentation in the deep sea is represented by the BenthicImpact Experiments (BIEs) which have been conducted with similar experimental design by anumber of nations or multinational consortia. Since environmental impacts derivingfrom human penetration into the deep sea on an industrial scale are expected to besevere and long-lasting, a precautionary approach in the related environmental researchseems most appropriate. It is therefore proposed that environmental risk assessment in thedeep sea should rely on in-situ experiments which should start from a simulation ofsmall-scale impacts and proceed stepwise to the monitoring of a full-scale industrialoperation. At each stage impacts need to be evaluated thoroughly.

The response of large river systems to human development isoften hard to predict. The spatial scale of these systems makes themdifficult to study and their ecology (particularly in the case of largenorthern rivers) is often poorly understood. To provide an ecologicalassessment of three large river basins in northern Canada, the NorthernRiver Basins Study (NRBS) undertook a multi-disciplinary approach toassess environmental and socio-economic impacts of development. Resultspresented here focus on key findings relating to studies of fish healthwithin the basins. It was known at the outset of the NRBS that dioxins,furans and other organic contaminants would be present in the system.However, NRBS research indicated low levels of environmentalcontamination, particularly compared to other systems in Canada andelsewhere in the world. In addition, contaminant loads in fish generallyconform to Canadian guidelines for both aquatic and human health;although, levels of dioxins, furans, PCBs and mercury in biota didexceed guidelines at certain times and in certain locations. The weightof evidence indicates that many of the fish in these basins exhibitsigns of physiological stress. Of particular concern was the findingthat sex hormone levels in burbot and longnose sucker collected fromnear-field pulp-mill locations were significantly depressed, and thatnumbers of immature fish in these same locations were unexpectedly highand more likely to show external abnormalities. In addition, there is aperception that fish in the lower reaches of the Peace-Athabasca basinsand in the deltas are of lower quality. Studies of fish health have beenintegrated with other technical studies in a cumulative effectassessment and will provide a basis for future research and managementdecisions within these basins.

The VALIMAR project aims at identifyingbiomarkers in fish that are suitable to detectand predict environmental stress from chemicalpollution or from limnological parameters inthe field. For two small streams in SouthernGermany, concentration values of 31contaminants in water and sediment and 12 limnological parameters as well as 27 biomarkersmeasured in brown trout and stone loach werecollected. All these physicochemical andbiological parameters have been analysed forpatterns that discriminate between the streams,using discriminant analysis (DA), analysis ofvariance (ANOVA) and of covariance (ANCOVA), and principal component analysis (PCA) asmultivariate statistical techniques. Moreover,the biological data were analyzed with respectto species-specific patterns, and the partialleast-squares regression method (PLS) was usedto study the impact of chemical and limnological data on the health status of the targetspecies as characterized by the biomarker data.Abiotic as well as biotic data yielded goodseparations between the streams, with theultrastructure of gill (US-gill) being thestrongest discriminator variable among all 27biomarkers tested. With regard to the two fishspecies, the biomarker data from brown troutshow significantly greater differences betweenthe two streams than the biological responsesin stone loach. Application of PLS yieldssignificant regression models for only fewbiomarkers including US-Gill, which can bepartly traced back to significant noise levelsin the data set as quantified by permutationtests.

Effects of contaminants may occur at all levels oforganization, from molecular to ecosystem-levelresponses. While biochemical and physiologicalalterations in organisms may occur rapidly and areoften stressor-specific, the ecological relevance ofthese suborganismal indicators is uncertain.Alterations in populations and communities havegreater ecological relevance, but a firm mechanisticunderstanding of these responses is often lacking.Developing mechanistic linkages across levels ofbiological organization would greatly improve ourunderstanding of how organisms are affected bycontaminants in nature. The papers in this seriespresent several innovative approaches for integratingeffects of contaminants across levels of biologicalorganization. Authors were asked to describe theecological consequences of responses at lower levelsof organization (biochemical, physiological,individual) and to speculate on the underlyingmechanisms associated with population and communityalterations. The most consistent finding of the fivepapers in this series is that there is no singlespatiotemporal scale or level of biologicalorganization at which ecotoxicological investigationsshould be conducted.

The partitioning of trace metals and hydrophobic organic contaminants to phytoplankton determines their toxicity as well as their fate and transport in aquatic ecosystems. Accurate impact assessments, therefore, depend on a good understanding of the factors regulating the sorption of these compounds to biotic particles. The accumulation of chlorinated organic compounds in phytoplankton is generally considered as being due solely to physical sorption, described by reversible equilibrium models based on Langmuir or Freundlich isotherms. On the other hand, the uptake of trace metals is a two phase process: a fast sorption component viewed as an ionexchange or a covalent bonding process with cell surface ligands, followed by an intracellular transport phase that is dependent on cellular metabolic activity. The uptake of inorganic and hydrophobic organic pollutants and their bioaccumulation are influenced in a complex manner by duration of exposure and cell density, by environmental factors such as pH, the concentration of cations and of dissolved and colloidal organic matter, as well as by phytoplankton physiological condition. High concentrations of H+, Ca2+, and Mg2+ ions will reduce trace metal sorption by directly competing for uptake sites on the cell's surface, whereas the presence of dissolved organic carbon such as natural and synthetic chelators and phytoplankton exudates will reduce the bioavailability of both trace metals and hydrophobic organic contaminants. Thus, the impact of toxic contaminants on phytoplankton may be determined as much by the factors influencing uptake and partitioning as by the potency of the toxicants and interspecies differences in sensitivity. Recommendations for improving toxicity assessments are presented.

As a supporting component of the VALIMARproject, physicochemical investigations wereconducted monthly from 1995 to 1999 at theKrähenbach/Aich stream system (two samplingsites) and at the Körsch stream (sixsampling sites). Several physicochemicalparameters were analysed continuously bydataloggers during the entire sampling period.Moreover, a selection of the most importantmorphological parameters of the stream wererecorded in 1998. The results of these physicochemicalinvestigations demonstrated that theKrähenbach/Aich system could becharacterized as a natural rhithral submontanecarbonate stream system that is welloxygenated. Low temporal variations in pH,conductivity and chloride occurred at allsampling sites in the Krähenbach whichcoincided with the geological conditions atthis test stream. Because of relatively lowconcentrations of organic and inorganiccompounds during the entire study period thesites AB and AC in the Krähenbach/Aichsystem were classified as “slightly polluted”.The morphological assessment of the streamindicated a “moderately affected” status atboth of these streams. Physicochemical and morphologicalinvestigations along the Körsch streamsystem (KA to KE including the tributary streamSulzbach) indicated a highly affected rhithralsubmontane carbonate system characterized byhigh water velocity, flow rate and dissolvedoxygen. The Körsch, however, differssignificantly with respect to watertemperature, conductivity, pH, BOD5,nutrients, and chloride concentrations from theKrähenbach. As a result of differentanthropogenic inputs (e.g. several sewageplants, agriculture activities and waste waterdumping) the Körsch sites KA to KD wereclassified as “critically” to “heavilypolluted”. The morphological assessmentindicated a “clearly affected to damaged”status. The upstream site KE could becharacterized as “slightly polluted” and itsmorphological structure as “moderatelyaffected”.