Soft-bottom Macrofauna Research Articles

Relating species patterns and environmental variables by canonical ordination: An analysis of soft-bottom macrofauna in the region of Tromsø, northern Norway

Relationships between species composition and environmental variables in softbottom faunal communities near the city of Tromsø, northern Norway (69 ° 40′ N, 19 ° 0′ E), were examined using Canonical Correspondence Analysis (CCA). Quantitative data for 87 species and 14 environmental variables at 30 stations (21 sites) were considered. The variables used were depth, sediment parameters (grain size distribution, total organic carbon (TOC), C/N ratio), and an index representing organic effluent discharge. It was possible to explain roughly one-third of the species variance. Depth was the most important variable, but significant species patterns were also related to the effluents and to fine sand and gravel sediment fractions. The species assemblage at enriched stations was strongly associated with organic discharge and TOC, but relationships between species and effluents were also detected in areas not adversely affected by the organic discharge. The amount of unexplained species variance suggests that various other factors also influence species assemblages. Thus the use of CCA indicates the need to characterise different ecological relationships in order to interpret the biological information more completely.

Relationship between soft bottom macrofauna and polycyclic aromatic hydrocarbons (PAH) from smelter discharge in Norwegian fjords and coastal waters

Data from monitoring surveys were used to test the responses of soft bottom fauna in Norwegian fjords and coastal waters affected by effluents from aluminium and manganese alloy smelters to effluent discharges. Generally, polycyclic aromatic hydrocarbons (PAHs) have been considered the main threat to the biota in the receiving waters. Data from a total of 57 quantitative stations, of which 30 were simultaneously sampled for sedimentary PAHs, were analysed. Canonical Correspondence Analysis (CCA) was used to evaluate species patterns in relation to sediment PAH concentrations and natural environmental variables such as depth, sediment characteristics and riverine input. The PAHs varied from very high concentrations (760 pg g.' total PAH) at the most impacted sites to background levels in reference areas. Despite previous reports of little to no effects of the effluent discharges, the analyses identlf~ed significant species changes along PAH gradients, which could be associated with feeding modes. In particular, a number of carnivorous polychaetes had their dlstnbution ophma In the most affected areas. Based on species statistics calculated by CCA, response functions were fitted for the species on PAH and used to establish a generalised expression of trophic community structure in relation to PAH concentrations. At low PAH levels, the carnivores represented 15 to 20% of the specimens in the communities, but the proportion began to increase from about 10 pg g-' and exceeded 50% at 100 pg g-' total PAH. The fauna1 changes were most evident in shallow waters, possibly reflecting the effects of dissolved PAHs to which the species may react more directly than they do to sedlrnentary particle-associated PAHs.

Soft-bottom macrofauna and responses to organic enrichment in the subarctic wates of Tromsø, northern Norway

The soft-bottom macrofauna (> 1 mm) of Tromsøysund and Sandnessund near Tromsø, northern Norway (69°40′N, 19°0′E) was sampled quantitatively in 1983, 1990 and 1992 in order to assess enrichment effects from discharges of municipal sewage and fish factory effluents. The studies comprised 30 stations between 7 and 40 m depth at varying distances from effluent outfalls. In total 395 species/taxa were recorded. The polychaetes were the most important group both with regard to the numbers of species (146) and specimens (80% of total), but bivalves and amphipods were also common. Most stations had species numbers between 40 and 100 and densities between 2000 and 8000 ind. per m 2. The species assemblages could be related to organic enrichment, depth and sampling year. Evidence suggests that the organic discharges did not seriously affect the waters surrounding Tromsø, but the generally high abundances, the prevalence of polychaetes and a numerical importance of ‘opportunistic’ species ( Polydora, Chaetozone, Heteromastus) might suggest that the whole area was stimulated by the organic inputs. Sharply delimited strongly enriched zones characterized by dense populations of Capitella capitata were found on shallow sites close to large outfalls in Tromsøysund. These local and restricted effects of the discharges may be related to strong tidal currents and wave action that disperse effluent components. The faunal composition remained largely stable from 1983 to 1992 at 9 revisited stations, but the number of small bivalve and crustacean taxa increased and the abundance of the dominant polychaete Polydora socialis strongly decreased. The effluent discharges were supposed to have increased from 1983 to 1992, but the faunal changes did not provide evidence of an increased enrichment of the area during the period.

Soft-bottom macrofauna and responses to organic enrichment in the subarctic wates of Tromsø, northern Norway

Soft-bottom macrofauna and responses to organic enrichment in the subarctic wates of Tromsø, northern Norway

Impact of Two “El Niño” Events of Different Intensity on the Hypoxic Soft Bottom Macrobenthos off the Central Peruvian wast

. Monthly changes in the community structure of hypoxic soft-bottom macrobenthos have been studied at a station at 34 m depth in Ancon Bay (Peru) before and during two El Nino (EN) events. Of these events, 1982-83 is considered the strongest, and 1991–93 one of the most prolonged in the 20th century. On the oceanographic scale, EN 1982–83 ranges as “very strong”, whereas EN 1991–93 ranges as “moderate”. The thermal anomalies at the station during EN 1982–83 (+ 7.8 °C) were almost twice those of EN 1991–93 (+ 4.1 °C). However, the community changes were not in all cases proportional to the extent of warming. Species numbers increased in a similar way (up to 24 species from near zero in each of the two events), but maximum faunal density was five times higher, and mean biomass was twice as high in 1982–83 compared with the event a decade later. Species diversity was slightly higher during EN 1982–83, whereas successional and trophic changes occurred on a broader scale during EN 1991–93. On the whole, the impact of the long-lasting event on the small soft-bottom macrofauna was not much weaker than that of the exceptionally strong event. The authors discuss the mechanisms which may be responsible for the differences and similarities encountered in the benthic community dynamics during these two events. Both in the unusually strong and the unusually long EN, the community revealed a pattern of early biological response several months ahead of the onset of local warming which marks the official begin of EN. The question is addressed to what extent the increase of certain parameters in the benthic community could be used for predictive purposes.

Radioecological Research on the Marine Environment Facing the Italian Base in Antarctica (1989–91)

Abstract The results of the analysis of both natural (Th-232, U-238 and K-40) and artificial (Cs-137) radioactivity contained in samples collected during the 1989–90 and 1990–91 PNRA Scientific Campaigns in the Terra Nova Bay (Ross Sea) marine ecosystem, are presented in this paper. The data refers to samples of sea water, pack water, sediments and organisms belonging to demersal ichthyofauna (Pagothenia bernacchii, Chionodraco hamatus) and soft bottom macrofauna (Adamussium colbecki) collected in different coastal and off shore stations of the area investigated. Some sea water samples collected on the way to subAntarctic areas were also considered. The radiocontamination detected in sediments was correlated to the quantities of organic matter, organic carbon and nitrogen contained in the samples. Additionally, Cs-137 concentration factors were calculated for the different biological specimens and their anatomical components. Data values, with special consideration for anthropogenic Cs-137, are compared to results obtained from similar matrixes collected in the Northern Hemisphere in temperate waters before and after the accident at the Chernobyl nuclear plant.

Effects of an oil spill on the soft-bottom macrofauna of Arthur Harbour, Antarctica compared with long-term natural change

The macroinfauna at depths 30–115 m was sampled in March–April 1989, c. two months after an oil spill that resulted from the grounding of the Bahia Paraiso. Stations consisted of the oil-spill site and a comparable control location, and two historical sites previously sampled in 1971. The historical sites were located at two distinct points along a known continuum of increasing physical stability with depth, attributed to disturbances from glacial calving. Macroinfaunal assemblages at most stations were characterized by very high densities and numbers of taxa. There were no significant differences (P<0.05) between the oil-spill and control sites in numbers of individuals, species, or families; nor were there any major differences in dominant fauna or overall community composition. The absence of a detectable impact on the fauna is consistent with results of hydrocarbon analyses, which showed that subtidal sediments were nearly devoid of contamination emanating from the Bahia Paraiso. The assemblage at the shallower of the two historical sites, however, showed a substantial change over the 18-yr period between studies. This change consisted of a shift toward a more species-rich and abundant macroinfauna characteristic of the more physically stable parts of the harbour. This change may be related to the fact that the glacier face near this site has retreated c. 250 m over the last 20 yrs, resulting in less physical disturbance of the adjacent seafloor.

Long-term changes in soft bottom macrofauna in the Gulf of Bothnia-a sign of eutrophication

Long-term changes in soft bottom macrofauna in the Gulf of Bothnia-a sign of eutrophication

Environmental effects of a herring mass mortality in northern Norway. Impact on and recovery of rockyshore and soft-bottom biotas

Abstract In October 1984 a school of herring died in the small shallow bay of Alterosen, Lofoten, northern Norway. During the decay of the fish, subtidal sediments turned black from sulphides while fats and oils floated ashore covering seaweeds and rocks. In the subtidal the soft-bottom macrofauna was killed. Recovery took more than three years, following typical successional patterns. The polychaetes Capitella capitata and Scolelepis fuliginosa had high abundances during 1985 and 1986. Intertidal damage was limited. In the rocky shore the key algal species, Ascophyllum nodosum, tolerated the pollution, but encrusting algae and sponges, and epiphytes were locally affected. Intertidal sediment fauna was only affected during autumn 1984. The different impact and recovery of the intertidal and subtidal communities was found to be in marked contrast to other cases of long-term organic pollution. The results are discussed in view of various effects of stress and disturbance on communities.

Experimental recolonization by macrozoobenthos in a bay polluted by municipal sewage, oil and heavy metals compared to an unpolluted Baltic bay

Abstract Ambient communities and recolonization pattern of soft-bottom macrofauna was studied at two localities on the Swedish east coast (Baltic Sea). One was polluted by a steelworks and a municipal sewage treatment plant (Oxelosund), and the other was a reference site (Tvaren). The naturally occurring macrofauna at the polluted site was less diverse and had lower abundance and biomass compared to the reference site. These differences could, by deduction, be attributed to toxic effects of heavy metals, oils and/or PAH since there were no differences between the sites regarding depth, bottom substrate, oxygen, Eh, salinity or temperature. Recolonization by macrofauna in boxes containing an artificial sediment was faster at the polluted site. Abundance and biomass increased more rapidly and to a higher level compared to the reference site. This could be explained by enhanced nutrition conditions, measured as higher sedimentation rate and a higher nutritive value (organic content and nitrogen) of the sedim...

In-situ investigations on small-scale local and short-term changes of sublittoral macrobenthos in Lübeck Bay (western Baltic Sea)

In-situ studies on sublittoral soft bottom macrofauna (depth: 14–16 m) employing the underwater laboratory (UWL) “Helgoland” were carried out. Sets of samples were compared for small-scale local and short-term changes in species richness, faunal abundance, numerical dominance, diversity, evenness, homogeneity, and similarity. It could be shown that minor differences in sediment quality can cause conspicuous heterogeneity within a small sampling area (diameter: ca. 100 m). Both spatfall and mortality of benthic invertebrates can change the faunal structure within a short period (two months). The degree of change varies between species and thus at stations harbouring different faunal assemblages as well.

Observações preliminares sobre a fauna bêntica de sedimentos moles da baia de Santos e regiões vizinhas

The purpose of this paper is to give a preliminary qualitative assessment of the soft bottom macrofauna of the Bay of Santos and adjacent areas. Sixty-three samples were taken by the 'Emilia' with grab and otter trawl gears. 149 different species of benthic animals were collected, of which 52 were polychaets, 26 lamellibranchs, 20 echinoderms, 17 crustaceans, 14 gastropods, 4 cnidarians and 16 belonging to other taxonomic categories. The most frequent species were the polychaets Audouinia tentaculata, Poecilochaetus australis, Onuphis quadricuspis, Owenia fusiformis, Telepus setosus and Telepsavus costarum. The gastropod Littoridina australis var. nana occurred in high densities in the samples collected in the inner part of the Santos channel. Ophiactis lymani was found to be the most widely distributed ophiuran in this region. The lamellibranchs Mesodesma inactroides, Tivela mactroides, Donax hanleyanus and the thalassinid Callianassa major are common in the sand beaches of the bay. In the mangrove region numerous decapods occurred of the following genera: Uca, Ucides, Aratus, Metasesarma, the Maria mulata, crab Goniopsis cruentata, etc. Five different station groups and two more areas may be recognized in the region of the Bay of Santos and the homonimous channel.