Soft-bottom Macrobenthic Communities Research Articles

Minimal sampling requirements for a precise assessment of soft-bottom macrobenthic communities, using AMBI

Since AMBI was published originally in 2000, it has been used in an increasing number of investigations with monitoring purposes, or to analyse impacts on soft-bottom macrobenthic communities. Some guidelines for its correct use were published in 2005; however, a main issue remained without an answer — which are the minimal area and number of replicates necessary, to obtain a precise estimate for AMBI? In this study, new methodologies such as bootstrap techniques have been applied to this particular problem. Data were obtained from sampling carried out in 1995, within the framework of the Littoral Water Quality Monitoring and Control Network of the Basque Country (northern Spain). The sampling strategy consisted of 11 intertidal estuarine sampling stations (0.25m 2, sampled for each of six replicates) and 17 subtidal estuarine and coastal sampling stations (0.125m 2, sampled for each of six replicates). Two replicates have been established as being sufficient, both for intertidal and subtidal sampling stations, to classify 80% of the pseudosamples into the same disturbance level, in terms of AMBI, for 64% of the stations. For the minimal area, it has been determined also (for both intertidal and subtidal sampling stations) that 0.25m 2 is sufficient to classify 80% of the iterations into the same disturbance level, for 64% of the stations.

Soft-bottom macrobenthic community composition and biomass in a Posidonia oceanica meadow in the Ligurian Sea (NW Mediterranean)

A soft-bottom community (6–8 m depth) within a seagrass bed in Prelo Bay (Eastern Ligurian Sea) was studied between April 1990 and August 1991. Samples were collected using a suction device and were sieved through a 1-mm mesh size. Cluster analysis showed seasonal fluctuations in the macrofauna density with highest values in summer 1990 (maximum 2870.0 ± 2029.4 ind. m −2 in August 1990) and lowest in late spring 1991 (100.0 ± 37.8 ind. m −2 at the end of May 1991). On the whole, the community was characterised by a high number of species (184 species plus 17 higher taxa) but only 12 accounted for 78% of the total density, so diversity was relatively low. Dissimilarity between seasons was high (on average 74.7 ± 8.3) and the principal discriminating species was the amphipod Siphonoecetes dellavallei, whose successful recruitment dominated community density in summer 1990. Total macrofauna biomass ranged between 166.1 ± 67.8 mg AFDW m −2 (May 1991) and 2399.8 ± 1073.2 mg AFDW m −2 (June 1991); molluscs being the major contributors (ca. 61%) with single large individuals. Secondary production reached on average 0.4 ± 0.2 g C m −2 y −1. Notwithstanding the relative low biomass, deposit-feeders were the major contributors to secondary production (38%), indicating their high efficiency in utilizing their food resource (detritus-associated bacteria). The seagrass bed seems to play only an indirect role in the structure and function of macrofaunal assemblages.

Soft-Bottom macrobenthic communities of the Vitória Bay estuarine system, South-eastern Brazil

The present work describes and analyses the structure of the macrobenthic epi- and infaunal assemblage of the estuarine system of Vitória Bay, South-eastern Brazil, from January 1998 to June 1999. Replicated sampling at intertidal and subtidal levels was conducted quarterly at ten stations. Intertidal and subtidal sediment composition was characterised. Water physico-chemical parameters were measured in situ. A total of 10,695 individuals, belonging to 144 taxa, were collected. Molluscs, crustaceans and polychaetes were the most abundant groups. The bivalves Anomalocardia brasiliana, Mytella guyanensis and M. falcata were the most abundant species. Locally, significant discharges of residential and industrial wastewater resulted in high organic content in the sediment (up to 30%) and low dissolved oxygen concentration in the water (< 1mg.l-1). Near the two entrances of the bay, high hydrodynamic activity and coarse sand reduced the detrimental effects of raw and treated sewage inputs. Species richness (S), diversity (H') and total abundance (A) decreased from outer-bay stations (22 < S < 72; 1.99 < H' < 2.85; 320 < A < 1737) towards inner-bay stations (2 < S < 45; 0.59 < H' < 2.67; 2 < A < 1317), where salinity and dissolved oxygen were lowest and organic matter content highest.

Seasonal variation of macrobenthic infauna in the Johor Strait, Singapore

Sediment samples were collected every three months from December 2001 to December 2002 to study the seasonal variation of soft-bottom macrobenthic community at a site (1°25′30′′N, 103°52′00′′E; depth: 6.5 m) in the Johor Strait, Singapore. Seasonal changes in species number, abundance and diversity of macrobenthic infauna significantly differed, the lowest values for the three parameters were recorded in December, the highest values for species number and species diversity in March and the highest abundance in September. Species composition and community structure also varied gradually over time. The differences in dominant species and community structure between December 2001 and December 2002 suggest an interannual variation of macrobenthic infauna.

Oxygen levels versus chemical pollutants: do they have similar influence on macrofaunal assemblages? A case study in a harbour with two opposing entrances

Generally, harbours are polluted zones characterised by low values of hydrodynamism and oxygen in the water column and high concentrations of pollutants in sediments. The harbour of Ceuta, North Africa, has an unusual structure; it is located between two bays connected by a channel, which increases the water movement and exchange in the harbour, maintaining moderate oxygen levels in the water-sediment interface. Nevertheless, high concentration of organic matter, nutrients and heavy metals were measured in sediments from this harbour. Under these unusual conditions (high levels of pollution but total saturation of oxygen in the water column) we studied the responses of soft-bottom macrobenthic communities using uni and multivariate analyses. The number of species was similar inside and outside the harbour but the species composition differed between internal and external stations; oxygen levels seem to control the ‘quantity’ of species whereas pollutants control the ‘quality’ of them.

Spatiotemporal variation in benthic polychaetes (Annelida) and relationships with environmental variables in a tropical estuary

Annelida constitute a dominant functional component in soft-bottom macrobenthic communities and reveal a wide range of adaptability to different marine and coastal habitats. Analyses in different polychaete assemblages and their responses to habitat conditions reflect the biological effects of marine pollution and habitat disturbance. The present study is designed to study colonization and community structure of polychaetes in two ecologically distinct locations of the Sundarban Biosphere Reserve on the northeast coast of India. Polychaete assemblages are characteristically different at the two sites in the extreme northern (Ghusighata) and southern (Gangasagar) portions of the Biosphere Reserve. Levels of heavy metals in polychaete body tissues also reveal interspecific and regional variations. The predominant polychaete fauna exhibited a distinct and unique assemblage of two types: (i) Mastobranchus indicus – Dendronereides heteropoda in the sewage-fed substratum at Ghusighata and (ii) Lumbrinereis notocirrata – Ganganereis sootai – Glycera tesselata at Gangasagar at the mouth of the Hugli estuary where chronic anthropogenic stress and contamination with agricultural and industrial effluents occur. The faunistic composition of polychaetes and their potential for the accumulation of heavy metals from the ambient medium are distinctly different. The study demonstrates that textural composition of the sediments, together with hydrodynamic and geotechnical properties, seem to have the greatest control to quantify the differences of the polychaete community in the two study stations. An in-depth comparative study of polychaete community structure at multiple spatial scales is strongly recommended for future environmental impact assessment in this fragile environment.

The relationship between soft-bottom macrobenthic communities and environmental variables in Singaporean waters

Univariate and multivariate methods were used to study soft-bottom macrobenthos collected in December 2002 from the coastal waters of Singapore. The univariate parameters and community structure of benthic communities were related to environmental variables. Three samples were taken with a 0.1 m 2 Van Veen grab (33 × 30 × 15 cm) at each station from 12 sampling stations of two different geographical areas. The water depth ranged from 6.5 m to 34.0 m. The mean values of species number, abundance and species diversity ( H′) were 24 species/grab, 77 animals/grab and 3.35/grab, respectively. A total of 172 species was recorded. Total petroleum hydrocarbons were strongly negatively related to species number, abundance and species diversity, suggesting that petroleum hydrocarbons have harmful effects on macrobenthic communities. The BIO-ENV analyses for all stations identified median particle size, silt–clay content, salinity and Zn as the major environmental variables influencing the infaunal patterns. However, separate analyses for two areas produced stronger correlations and different best-correlated environmental variable combinations. Total petroleum hydrocarbons were the only common factor in both areas, showing the importance of petroleum contamination in determining the community structure of benthic infauna in Singaporean waters.

Seasonal Dynamics of Soft Bottom Macrobenthic Communities of the Sublittoral in Peter the Great Bay, Sea of Japan

Seasonal dynamics of macrobenthos were studied at five stations located at depths of 10–60 min in the Far East State Marine Reserve (southern Peter the Great Bay) during 1984–1987. Sampling was conducted at stations once per season. Stable seasonal fluctuations of the population density and the biomass in basic taxonomic groups were found. As a rule, the quantitative parameters were augmented in spring and summer, and decreased in fall and winter. This was caused, first of all, by summer fluctuations of the number of small and short-lived species of polychaetes and bivalve molluscs. The amplitude of fluctuations decreased with increasing depth. Variation in the quantitative parameters was significant at the community level only at the most shallow-water stations. It was assumed that this phenomenon might be caused by the seasonal consumption of macrobenthos by bottom fish and by the periodicity of detritus supply to the bottom from the water column with a background of varying environmental temperature parameters and of mass settling of benthic larvae. The seasonal changes in parameters began and ceased earlier in 1986–1987 than 1984–1985, which was related to an appreciable decrease in water temperature in 1986. During the period of study, an increasing trend of parameters, apparently part of a long-term cycle, was recorded both for individual groups and for entire communities, and was the most appreciable at greater depths (47–60 m).

Structure and Secondary Production of a Soft Bottom Macrobenthic Community in a Brackish Lagoon (Sacca di Goro, north-eastern Italy)

The composition and distribution of the macrobenthic community in a lagoon in the Po River delta was investigated by taking monthly samples at three sites during 1994. A total of 38 macroinvertebrate taxa, representing five phyla, were identified. Gastropods, amphipods, and chironomid larvae dominated the macrofauna in term of abundance, while in terms of biomass bivalves were the dominant taxon. Monthly total invertebrate abundance showed considerable fluctuations, depending on the season and on the presence of the red macroalgae Gracilaria verrucosa. In the central area of the lagoon, a significant relationship was demonstrated between macrobenthic community parameters and amount of macroalgal cover. Taking the most important species, i.e. those that contributed most to similarity within sites, only Cerastoderma glaucum was found to be negatively related to the amount of macroalgal biomass. Mean annual secondary production varied between 50 and 75g AFDW m−2yr−1depending on the site, yielding P/B ratios between 1·02 and 1·08. Confinement and moderate disturbance due to the presence of algal cover are hypothesized to determine structure, composition, and production of the macrobenthic community in the Sacca di Goro.

Amphipods are Good Bioindicators of the Impact of Oil Spills on Soft-Bottom Macrobenthic Communities

The Amoco Cadiz oil spill in 1978, and the Aegean Sea oil spill in 1992, affected soft-bottom communities, respectively from the Bay of Morlaix (western English Channel) and from the Rı́a de Ares and Betanzos in the north-western Iberian peninsula. These infralittoral communities on muddy fine sand showed similar species composition and structure and occurred in similar hydro-climatic conditions. The effects of the spills were identical in both areas with the disappearance of the amphipods especially those from the amphipod genus Ampelisca with a very low colonization of these species during the four years after the spill. The recovery rate of the amphipods was slow but progressive. In such communities no proliferation of opportunistics was observed after the stress. In the sites, where polychaetes dominated before the spill, they remained dominant, whereas other sites showed very low total abundances during the two years after the spill due to the absence of compensation for the disappearance of these crustaceans. In fact, there was a very low impact of the spill on polychaetes, but a high one on amphipods. In the future, it is suggested to focus monitoring after a spill only on a single amphipod group proposed as a bioindicator for detecting the impact of pollution. A polychaete/amphipod ratio is proposed to reflect temporal change of soft-bottom communities analogous to the nematode/copepod previously suggested for the meiobenthos. Detailed knowledge of the qualitative and quantitative structure of a benthic community is still needed in order to identify very precisely the effect of a pollution event.

Intra-annual Variability in Hawaiian Shallow-water, Soft-bottom Macrobenthic Communities Adjacent to a Eutrophic Estuary

Temporal variability in shallow-water (10m), soft-bottom macrobenthic communities was examined over a period of 25 months (November 1992–November 1994) off-shore of the Ala Wai canal, a tropical eutrophic estuary on the south shore of O'ahu, Hawaii. Despite significant temporal variations in the density of major taxonomic groups at the four stations examined, there was no evidence of a regular seasonal signal in the density fluctuations. Although all stations showed a steady decline in mean density during the unusually dry period in the spring of 1993, there was no evidence that observed macrofaunal density fluctuations (maximum and minimum) were associated with periods of increased runoff. Intensive macrobenthic sampling after a large runoff event showed no evidence that the event influenced the density or community composition of the benthos over a two month period. Total macrofaunal density ranged from 491 to 4743ind.0·1m−2with total macrofaunal biomass ranging from 4·7 to 109mg AFDW 0·1m−2(AFDW—ash free dry weight), values consistent with those of other tropical and subtropical studies. A significant between-year difference in the density of total macrofauna was observed, perhaps associated with the 1991–1994 El Niño Southern Oscillation (ENSO) event and the corresponding decreased rainfall in Hawaii.

Do climatic oscillations influence cyclical patterns of soft bottom macrobenthic communities on the Swedish west coast?

Do climatic oscillations influence cyclical patterns of soft bottom macrobenthic communities on the Swedish west coast?

Comparative study of the structure of some tropical and temperate marine soft-bottom macrobenthic communities

Macrobenthic sampling of a transect of six stations on the North coast of Central Java in October 1985 revealed three distinct communities which can be regarded as paraliels of those from north temperate waters: (i) An Amphioplus (Lymanella) laevis/Lovenia sp. community parallel with the Amphiura chiajei/Brissopsis lyrifera community. (ii) A Tellinides timorensis community parallel with Tellina spp. communities. (iii) A Laciolina philippinarum community parallel with Macoma spp. communities. A strict comparison of the structure of the first two of these communities with their counterparts in England shows that within-habitat diversity is similar in both regions. Diversity at two shallower subtidal stations is higher than at two deeper stations: this is attributed to the effects of natural, low-level, physical disturbance which maintains the communities in a sub-climax stage. Total abundance and biomass of the macrobenthic fauna was lower at the Javanese stations than in their temperate counterparts.

Competitive organization of the soft-bottom macrobenthic communities of southern California lagoons

The sandy-bottom macrobenthic community of Mugu Lagoon, a relatively pristine southern California (USA) marine lagoon, demonstrated (1) nearly constant community composition over 37 months of observation, (2) relatively little temporal variability in the population densities of the most abundant species over 37 months, and (3) a pattern of depth stratification in which very little vertical overlap existed among the six most abundant species. The only two species whose vertical distributions overlapped broadly showed horizontal spatial segregation, each abundant in different areas within the sand habitat. These community characteristics imply the importance of biological factors in structuring the sand benthos. The relatively large volume required for living space by these macrofauna suggests that competition for space may be the biological factor most important in determining the observed temporal and spatial abundance patterns. The muddy-sand community and the mud community of Mugu Lagoon also revealed similar patterns of stratification: new abundant species replaced species at the same sedimentary level while not greatly affecting species populations at other non-overlapping levels. In the sand community of Tijuana Slough, two of the abundant species of Mugu Lagoon's sand community were nearly absent as an apparent result of human over-exploitation. Probably in response, densities of species living at the sedimentary levels normally occupied by the missing species were much higher than would be predicted if competition for space were unimportant. In field experiments, removal of the deposit feeder Callianassa californiensis resulted in high recruitment of Sanguinolaria nuttallii, whereas control areas showed no S. nuttallii recruitment. Experiments also suggest that negative intraspecific interactions between Cryptomya californica individuals may explain the observed rapid emigration from areas of artificially high density. Perhaps the relatively great environmental predictability of southern California lagoons has permitted competitive interactions to play a singnificant role in determining the temporal and spatial abundance patterns of the soft-bottom macrobenthos.

Effects of Tropical Storm Agnes on Soft-Bottom Macrobenthic Communities of the James and York Estuaries and the Lower Chesapeake Bay

Macrobenthos was studied at 58 previously surveyed stations following the drastic salinity reductions caused by Tropical Storm Agnes. Effects were greatest in the lower, polyhaline portions of the James and York estuaries, where many abundant species were eliminated from shallow bottoms due to the usually low salinities and several species were eliminated or reduced in abundance on deeper bottoms due to the somewhat reduced salinity but, more importantly, to low oxygen concentrations resulting to strong density stratification of the water masses. Irruptions of opportunistic species followed these perturbations and the deep mud bottom community in the lower York estuary had not recovered 2 1/2 years after the storm. The primary alteration to usually mesohaline communities was an infusion of species more abundant in oligohaline and/or shallow brackish habitats. Communities in usually, oligohaline or tidal freshwater reaches of the James and York estuaries and those at the mouth of the bay were hardly affected by Agnes.