Brage Rygg

Distribution of species along pollution-induced diversity gradients in benthic communities in Norwegian fjords

Abstract The main aim of the present study was to detect species indicative of pollution impact on communities of soft-bottom fauna in Norwegian fjords. The work was based on the assumptions that increased pollutant load and lowered diversity are correlated and that different species respond differently to pollution. Low diversity was caused by high dominance of a limited number of opportunistic species capable of reaching high densities in adverse environmental conditions, and by the recession of a number of species intolerant of such conditions. Pollutant load was a main cause of these structural changes. Classification of 100 common species according to their distribution along a diversity gradient comprising 150 stations are presented. About 45 species were significantly absent from the low-diversity stations. The presence of one or more of these species will indicate that the pollution impact is low or moderate. Certain groups of species can by collective absence indicate, if within a defined zoogeographical area, that the pollution impact is high.

Response of single benthic metrics and multi-metric methods to anthropogenic pressure gradients, in five distinct European coastal and transitional ecosystems

In recent times many benthic indices have been proposed to assess the ecological quality of marine waters worldwide. In this study we compared single metrics and multi-metric methods to assess coastal and transitional benthic status along human pressure gradients in five distinct environments across Europe: Varna bay and lake (Bulgaria), Lesina lagoon (Italy), Mondego estuary (Portugal), Basque coast (Spain) and Oslofjord (Norway). Hence, 13 single metrics (abundance, number of taxa, and several diversity and sensitivity indices) and eight of the most common indices used within the European Water Framework Directive (WFD) for benthic assessment were selected: index of size spectra (ISS), Benthic assessment tool (BAT), Norwegian quality index (NQI), Multivariate AMBI (M-AMBI), Benthic quality index (BQI), (Benthic ecosystem quality index (BEQI), Benthic index based on taxonomic sufficiency (BITS), and infaunal quality index (IQI). Within each system, sampling sites were ordered in an increasing pressure gradient according to a preliminary classification based on professional judgement. The different indices are largely consistent in their response to pressure gradient, except in some particular cases (i.e. BITS, in all cases, or ISS when a low number of individuals is present). Inconsistencies between indicator responses were most pronounced in transitional waters (i.e. IQI, BEQI), highlighting the difficulties of the generic application of indicators to all marine, estuarine and lagoonal environments. However, some of the single (i.e. ecological groups approach, diversity, richness) and multi-metric methods (i.e. BAT, M-AMBI, NQI) were able to detect such gradients both in transitional and coastal environments, being these multi-metric methods more consistent in the detection than single indices. This study highlights the importance of survey design and good reference conditions for some indicators. The agreement observed between different methodologies and their ability to detect quality trends across distinct environments constitutes a promising result for the implementation of the WFDs monitoring plans. Moreover, these results have management implications, regarding the dangers of misclassification, uncertainty in the assessment, use of conflicting indices, and testing and validation of indices.

Chlorinated aromatic hydrocarbons in fish from an area polluted by industrial effluents.

The content of chlorinated fat-soluble aromatic hydrocarbons was determined in fish from an area polluted by industrial effluents. The fish species investigated were selected among those used for human consumption. For some samples, both the fillet and liver were investigated. For others the whole fish was used. The following compounds were analysed and quantified: Trichlorobenzene, tetrachlorobenzene, pentachlorobenzene, hexachlorobenzene, heptachlorostyrene, octachlorostyrene and polychlorinated biphenyls. The results idicate an appreciable accumulation in fish of the higher chlorinated compounds as pentachlorobenzene, hexachlorobenzene, heptachlorostyrene and octachlorostyrene. Other chlorinated hydrocarbons as decachlorobiphenyl, pentachloronaphthalene, hexachloronaphthalene and hexachlorostyrene were identified, but not quantified. The total content of fat-soluble chlorine was determined in some samples before and after sulphuric acid treatment. The content of chlorine in the identified and quantified compounds accounted for between 40 and 100 per cent of the total amount of chlorine present in the samples as persistent (sulphuric acid resistant) compounds.

Assessment of marine benthic quality change in gradients of disturbance: Comparison of different Scandinavian multi-metric indices

Three multi-metric benthic macrofauna indices were used to assess marine benthic ecological quality status (EcoQS) according to the European Water Framework Directive, in seven pollution gradients mainly, western Scandinavia. The impacts included organic load, hypoxia, metals, urban effluents and physical disturbance. The indices responded in a similar threshold fashion, irrespective of impact factor identity. Usually, the border between Good and Moderate EcoQS (G/M), is determined as some deviation from a reference situation. References, however, are difficult to find. An alternative procedure is described to estimate the G/M border, not requiring reference data. Thresholds, where faunal structure deterioration commences, were identified from non-linear regressions between indices and impact factors. Index values from the less impacted side of the thresholds were assumed to come from environments of Good and High EcoQS, and the 5th percentile of these data, was defined as the G/M border. Estimated G/M borders compared well with previous studies.

Heavy-metal pollution and log-normal distribution of individuals among species in benthic communities☆

Abstract The distribution of the number of individuals among species in benthic communities usually fits the log-normal. Organic pollution may lead to increased abundance of some species and a deviation from the log-normal. The hypothesis that heavy-metal pollution does not cause deviation from the log-normal was tested. The study was based on data from benthic-fauna investigations in Norwegian fjords polluted by heavy metals. Correlation between elevated sediment copper and lowered faunal diversity had been found there. The results indicated that the two distribution categories (fit to log-normal; deviation from log-normal) were unrelated to sediment copper and faunal diversity. Although frequently used as a method for detecting organic pollution impact on benthic communities, the test for log-normal distribution will be insufficient or inferior to a diversity index in detecting community changes induced by heavy-metal pollution.

Can benthic foraminifera serve as proxies for changes in benthic macrofaunal community structure? Implications for the definition of reference conditions

Benthic macrofauna is one of the most widely used biological groups to assess the ecological status of marine systems. Lately, attention has been paid to similar use of benthic foraminifera. In this study, distribution patterns of benthic foraminiferal and macrofaunal species were investigated simultaneously in 11 fjords in southeastern Norway in order to assess correlations and responses to environmental conditions. Selected fjords allowed to investigate contrasted environmental conditions from low total organic carbon (TOC) content (sediment TOC < 2.7%) in normoxia (bottom-water [O2] > 2 mL O2.L-1) up to high TOC content (> 3.4%) in severe hypoxia (< 0.5 mL O2.L-1). Environmental parameters comprised bottom-water dissolved oxygen, grain size, total organic carbon, total nitrogen (TN), pigments and depth below threshold (DBT). Foraminiferal and macrofaunal community data were significantly correlated (Procrustes analysis m2 = 0.66, p = 0.001). Hence, benthic foraminiferal distribution patterns mirror those of benthic macrofauna. However, as opposed to the foraminifera, macrofauna was not recorded at the most oxygen-depleted stations and, hence, was more sensitive to severe oxygen depletion. With regard to assigning species to ecological groups for ecological quality status assessment, the results suggest that species, e.g. Spiroplectammina biformis (foraminifera), Scalibregma inflatum (macrofauna), may exhibit different ecological requirements depending on their habitat. Considering the observed congruent patterns of benthic foraminifera and macrofauna, palaeo-communities of benthic foraminifera could be used as indicators of reference conditions for benthic macrofaunal community structure. This would however need further developments of algorithms to perform such a translation.