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Is Corophium Multisetosum Stock, 1952 an Exotic Invasive Species in Europe? Distribution, Habitat, and Recent Observations in the Netherlands
Abstract
Corophium multisetosum Stock, 1952 has been found in several estuaries and water bodies in Europe ranging from fresh and brackish to salt water. The species appeared to be distributed over a wide geographic range from the Iberian Peninsula to the southern Baltic region and is recently found in the Mediterranean and Gulf of Mexico, showing remarkable differences in ecology between populations. The recorded observations of the species in the Netherlands, however, remained restricted to a few smaller waters, and were published in grey literature. Recently, the species has been observed in a variety of waters in the southwestern part of the Netherlands and appears to be relatively common. The current study gives an overview of the recordings of C. multisetosum within its geographic range and its habitat preferences.
The recent observations on distribution and habitat preferences of C. multisetosum in the Netherlands are compared with the findings in other parts of Europe. Seeming discontinuities in recorded ecology of the species in the Netherlands and over Europe are discussed. C. multisetosum appears to be very flexible in its behaviour and appears to tolerate a broad range of environmental conditions. Local environmental conditions (e.g., salinity and substrate) and related communities (in the Netherlands particularly the presence of the seemingly competing species Corophium volutator (Pallas, 1766) and Chelicorophium curvispinum (G. O. Sars, 1895)) determine the presence of C. multisetosum and the local behaviour and abundance of the species in the system. As the species shows a typical distribution pattern with many recent recordings, its origin and possible dispersal routes are discussed.
... It was recorded already in the 1904 in UK and in the 1920s in the Netherlands. The species appears to be distributed over a wide geographic range from the Iberian Peninsula to the southern Baltic region (Wijnhoven et al. 2011), in the latter region it was found for the first time in 1962 in a brackish water basin in Poland (Jażdżewski 1976). It is recently found in the Mediterranean and Gulf of Mexico, showing remarkable differences in ecology between populations, and is both referred to as a warm-water species in the Baltic and as a cold-water species in Portugal (Wijnhoven et al. 2011). ...
... The species appears to be distributed over a wide geographic range from the Iberian Peninsula to the southern Baltic region (Wijnhoven et al. 2011), in the latter region it was found for the first time in 1962 in a brackish water basin in Poland (Jażdżewski 1976). It is recently found in the Mediterranean and Gulf of Mexico, showing remarkable differences in ecology between populations, and is both referred to as a warm-water species in the Baltic and as a cold-water species in Portugal (Wijnhoven et al. 2011). In the Nordic countries, the species was reported from Denmark in 2002 (Wijnhoven et al. 2011), and from Sweden in 2013 (Dyntaxa 2020). ...
... It is recently found in the Mediterranean and Gulf of Mexico, showing remarkable differences in ecology between populations, and is both referred to as a warm-water species in the Baltic and as a cold-water species in Portugal (Wijnhoven et al. 2011). In the Nordic countries, the species was reported from Denmark in 2002 (Wijnhoven et al. 2011), and from Sweden in 2013 (Dyntaxa 2020). It is nowadays considered an endemic species of the northeast Atlantic region (Buckley et al. 2004). ...
Two new amphipods for Norway Melita nitida and Corophium multisetosum (Crustacea; Amphipoda) were registered in brackish waters in the Tista Estuary in Halden, southeastern Norway. Both species were found in the samples from Tista’s outlet into the Idde Fjord, C. multisetosum in the beach zone and M. nitida at about 4 m depth. Melita nitida is a North American species first found in Europe in the Netherlands in 1998, and since then dispersed into the Baltic Sea via the Kiel Canal and now also found several places on the German Baltic Sea coast and in the Black Sea. Corophium multisetosum was collected even before the 1920s in Western Europe, and is considered native for Europe, whereas its relationship to North America is more ambiguous. From the British Isles and the Netherlands, it seems to have spread to Germany, Poland, Denmark and Sweden, and at present Norway. Until now the two species were found in small numbers at the Norwegian sites and their influence on the total benthic community is probably negligible in this initial phase. The Tista Estuary in Halden apparently appears to be a hotspot for alien brackish water species in Norway. Generally estuaries, with their combination of brackish water jointly with their unsaturated ecological niches and intensive international ship traffic, seem to possess the highest potential infection rate for aquatic systems with alien acrozoobenthic species.
... For instance, when it was found for the first time, it was misidentified as Corophium multisetosum Stock, 1952 by Ardisson andCastillo-Fernández (2004), an unrecorded species in the Gulf of Mexico so far. Later studies in the area continued reporting the new species as C. multisetosum (Rodríguez-Pliego et al. 2011;Wijnhoven et al. 2011). The present study contributes to clarify this misunderstanding. ...
A new species of the genus Caribboecetes Just, 1983 is described and illustrated from specimens collected on sandy bot-toms of the northern Yucatan Peninsula, southeastern Gulf of Mexico. Caribboecetes progreso sp. nov. differs from the closely related species Caribboecetes barbadensis Just, 1983 and Caribboecetes jenikarpae Just, 1984 by the inflated tri-angular anterolateral flange on basis of gnathopod 2, and from Caribboecetes justi Ortiz & Lemaitre, 1997 by the setose anterolateral surface of coxal plate 7 and basis of pereopod 7. Ecological notes for the new species, a morphological com-parison, map of distribution and key for all members in the genus are also provided.
The introduction of non-indigenous species (NIS) is one of the main reasons for the loss of biodiversity worldwide. This phenomenon has increased dramatically in recent decades leading to a reduction of the availability of ecosystem goods and services. One of the most important invasive species in aquatic ecosystems is the Asian clam, Corbicula fluminea (Müller, 1774). In this work, we compared the benthic macroinvertebrate assemblages in the freshwater section of two river estuaries, Lima and Minho, which were invaded with a 12-year gap by this non-indigenous bivalve. This study shows that C. fluminea’s
presence can model other species’ abundance in a strong fashion, especially in the later stages of invasion when it is fully settled. Although our results showed that the abundance of this invasive bivalve is linked to high values of biodiversity and to direct increases in the abundance of Gastropoda, an invasion by C. fluminea seems to prompt negative effects on specific crustacean species, such as the abundant amphipod species Corophium multisetosum. We propose that the dominance of one competitive species, coupled with favourable abiotic factors, may hinder the progress of C. fluminea’s invasion.
Guia marine outfall is the largest sewage discharge system in Portuguese waters. It serves four municipalities and a population of approximately 600,000 inhabitants. Effluent diffusion occurs approximately 3Km from the shore, at a depth of 40 meters. Operation of the outfall was initiated in May/June 1994 and, at present, does not include secondary treatment, or conventional primary treatment. In March 1994, before operation of the outfall, an integrated monitoring program was designed, which included a baseline sediment survey. Environmental chemistry, macrofaunal benthic communities and laboratory sediment toxicity analyses were performed in sediments from 20 sampling sites. These sites were revisited 3 and 4.5 years later in order to evaluate any changes to the sediments and their associated biota. This paper presents the results obtained from those two sampling periods, and proposes a classification for the evolution of sediment status. It also addresses the need or not to introduce, at present, more elaborate effluent treatment methods.
Interlaboratory variability was studied for the bioassay using crustacean amphipods. Nine series of data were obtained from different laboratories using four different species (Ampelisca brevicornis, Corophium volutator, Corophium multisetosum and Microdeutopus gryllotalpa), all previously used for sediment toxicity assessment in Spain. Results were studied for interlaboratory variability and according to different confounding factors. The coefficients of variation were similar to those previously reported for this bioassay and sample classification was homogeneous among the laboratories that succesfully completed the exercise. No significant tendencies related to test species were identified and it seems that the factor most critically affecting test results and the classification of samples is storage time before testing.
Crustacean news from Mecklenburg-Vorpommern. - In this study the recent distribution of the limnic Malacostraca of inland and coastal waters of Mecklenburg-Vorpommern were described. 29 species were observed. Especially for the glacial relict malacostracan species Mysis relicta and Pallasea quadrispinosa new knowledge will present. For Mecklenburg-Vorpommern first records were made for the allochthonous species Hemimysis anomala and Dikerogammarus villosus. Some other invasive species (Pontogammarus robustoides, Gammarus tigrinus and Dikerogammarus villosus) showed a wide dispersion during the last few years. The authochtonous species Gammarus lacustris and Synurella ambulans were pointed out. Within Germany both species have in Mecklenburg-Vorpommern their main distribution area. Due to the good adaptation on salinity conditions (fresh, brackish and marine) some brackish water species (Neomysis integer, Gammarus duebeni, G. zaddachi, Corophium lacustre, C. multisetosum) were included in this study.
1 -Coastal lagoons are particular ecosystems, since they are ecotones between terrestrial, freshwater and marine ecosystems, being characterized by a high temporal variability. Because of these characteristics, coastal lagoons have very peculiar abiotic and biotic conditions that require investigation if we are to understand their complex ecological functions. In this study, a list of invertebrate species from coastal lagoons in the Balearic archipelago is provided in order to enhance the knowledge of their aquatic fauna. This study reports on the existence of 123 species, from 135 genera and 24 families. The most common taxa were Chironomus spp. (Meigen, 1803) and Halocladius spp. (Hirvenoja, 1973) (Diptera, Chironomidae), Hydrobia ventrosa (Montgau, 1803) (Gastropoda, Hydrobiidae), Cyprideis torosa (Jones, 1850) (Ostracoda, Cytherideidae), Lekanesphaera hookeri (Leach, 1814) (Isopoda, Sphaeromatidae) and Naididae (Oligochaeta).
The upper limit of the distribution of Corophium volutator and the lower limit of the distribution of Salicornia europaea approximately correspond with mean high water of neap tide level (MHWNTL). Previous researchers concluded that the lower limit of S. europaea is determined by the higher frequency and duration of disturbance by tides and waves. At this site, moving water alone is not responsible for the absence of S. europaea below MHWNTL, the activities of C. volutator are important. Below MHWNTL there were fewer seeds, a greater proportion were buried and had failed to germinate than above MHWNTL. Some germinated seeds were present near the surface and the lack of established seedlings was attributed to disturbance by C. volutator. Seedlings transplanted to sediment sprayed with insecticide (to remove the amphipods) had a survivorship similar to those transplanted above MHWNTL, but twice those transplanted to unsprayed sediment. It was concluded that C. volutator prevent establishment of S. europaea partly by burial of seeds, but mostly by preventing establishment by seedlings, and in so doing reduce the stability of the sediment, increase erodability and lessen the prospects for successional development of salt marsh vegetation.
[The Kentish Stour Estuary has been subject to a continuous monitoring programme since June 1996. In September 1998, the exotic amphipod Chelicorophium curvispinum appeared in the upper, freshwater reaches of the estuary. At the same time, the population size of the native Corophium volutator dramatically increased in the lower part of the estuary. A third species, Corophium multisetosum, appeared near the limit of saline penetration in September 1999. Possible reasons for this multi-specific colonization, such as increases in salinity, temperature, chlorophyll a, and changes in anthropogenic impacts on the estuary, are discussed. L'estuaire du Stour à Kent, Royaume Uni, a été l'objet d'un programme continu de surveillance depuis juin 1996. En septembre 1998, l'amphipode exotique Chelicorophium curvispinum est apparu dans les eaux douces du cours supérieur de l'estuaire. Dans le même temps, la taille de la population indigène de Corophium volutator a augmenté de façon dramatique dans la partie inférieure de l'estuaire. Une troisième espèce, Corophium multisetosum, est apparue près de la limite de pénétration saline en septembre 1999. Les causes possibles de cette colonisation multi-spécifique, telles que l'augmentation de la salinité, de la température, de la chlorophylle a, et des modifications des impacts anthropiques sur l'estuaire sont discutées., The Kentish Stour Estuary has been subject to a continuous monitoring programme since June 1996. In September 1998, the exotic amphipod Chelicorophium curvispinum appeared in the upper, freshwater reaches of the estuary. At the same time, the population size of the native Corophium volutator dramatically increased in the lower part of the estuary. A third species, Corophium multisetosum, appeared near the limit of saline penetration in September 1999. Possible reasons for this multi-specific colonization, such as increases in salinity, temperature, chlorophyll a, and changes in anthropogenic impacts on the estuary, are discussed.
L'estuaire du Stour à Kent, Royaume Uni, a été l'objet d'un programme continu de surveillance depuis juin 1996. En septembre 1998, l'amphipode exotique Chelicorophium curvispinum est apparu dans les eaux douces du cours supérieur de l'estuaire. Dans le même temps, la taille de la population indigène de Corophium volutator a augmenté de façon dramatique dans la partie inférieure de l'estuaire. Une troisième espèce, Corophium multisetosum, est apparue près de la limite de pénétration saline en septembre 1999. Les causes possibles de cette colonisation multi-spécifique, telles que l'augmentation de la salinité, de la température, de la chlorophylle a, et des modifications des impacts anthropiques sur l'estuaire sont discutées.]
The community structure of the macrobenthic fauna (>0.5 mm) ofPotamogeton andMyriophyllum beds of the upper reaches of Canal de Mira (0.5−2) and of macrofauna density (369, 240 ind m−2).Potamopyrgus jenkinsi, Corophium multisetosum andLimnodrilus hoffmeisteri are dominant species in the study area. The community of station 1 includes an important set of taxa usually associated to freshwater habitats (oligochaetes, leeches and insect larvae) whilst in station 3 typically estuarine species (Cyathura carinata, Leptocheirus pilosus, Nereis diversicolor, Streblospio shrubsolii) occur. A succession of peak densities of different taxonomic groups during the year indicates seasonal variation in the community structure. The faunal assemblage of the study area is compared with similar ones in NE Atlantic and Mediterranean coastal systems.
The shallow-water fauna of 2 main channels in the Ria de Aveiro (Canal de Ovar and Canal de Mira) was sampled between June 1995 and June 1996 using a suprabenthic sled. Samples were collected monthly at 5 stations and every third month at 11 other stations, covering both channels from the lower to the upper reaches. The channels differ in their hydrodynamics, in the distribution of the sediment environments and in the salinity gradient, thus providing an invaluable example for field studies. The results presented herein concern peracaridan crustaceans. Multivariate analysis (MDS, ANOSIM and UPGMA) of the faunal data showed significant differences between the 2 channels. Spatial and seasonal variations within the channels were also significant. The distinctive structural features were the higher number of species and overall dominance of mysids in the Canal de Mira as opposed to the dominance of amphipods and higher densities in the Canal de Ovar. In both channels there was a spatial pattern of high densities in areas with a rich sediment environment (fine sediments, high organic content, more diversified and stable food sources). Specific life cycle features, unfavourable temperature and salinity conditions, and probably also increased predation pressure induced a general impoverishment of the peracaridan assemblage during winter. Amphipods (mainly epibenthic and tube dwellers) and mysids (characteristic suprabenthic) showed defined spatial and seasonal patterns. Amphipods dominated the areas with more stable food sources, while the highly motile mysids succeeded in colonising and dominated in more dynamic and unpredictable environments. Density fluctuations of amphipods and mysids occurred seasonally in non-coincident cycles. On the whole, mysids were dominant during winter and spring and amphipods during summer and autumn.
The spatial distribution of the subtidal crustacean assemblages of the Guadiana
River estuary was studied previous to the building of the Alqueva Dam (the
biggest dam in Europe). The differences between an estuarine and marine
environment seem to be the main reason responsible for the composition and
distribution of the crustaceans along the study zone. The Guadiana estuary has
shown high number of species in comparison with other nearby estuaries and this
richness seems justified by the scarce influence of pollutants (most of them
have shown low or moderate values) and their hydrodynamic and granulometric
characteristics (76 species were found, 39 in the estuarine area). A gradient of
enrichment and structuring of the assemblages was shown from the upstream to the
marine zones and a spatial segregation of species was found along this estuarine
environmental gradient, e.g. the amphipod Corophium
multisetosum and the isopod Cyathura carinata in the
upper estuary; the amphipod Bathyporeia cf.
pilosa and the isopods Lekanesphera levii and
Saduriella losadoi in the middle estuary; the amphipod
Melita hergensis in the mouth; and a high number of species
in the marine area. Since the Alqueva Dam will reduce the river discharges and
may cause changes in the abiotic characteristics such as granulometry of
sediments or salinity, this study establishes a baseline against which a
monitoring programme or follow-up studies could measure any significant effects
of the dam or related impacts.
Sandy bottoms, with local patches of rocks, dominate the southern Baltic Sea coast. These rock patches create three-dimensional habitats with additional niches that can support diverse assemblages of organisms. In this study we investigated macrofaunal assemblages associated with the boulder field in the brackish Gulf of Gdansk. Of the 30 recorded taxa three animal species (Mytilus trossulus, Balanus improvisus and Electra crustulenta) together with five species of algae were directly attached to rocks. These engineering organisms provided habitats for a further 22 taxa. Among the fauna directly associated with rocks, barnacles (76%) were the most abundant while among indirectly associated biota, oligochaetes were the dominant group (45%). Rock size and algal biomass explained most variance in macrofaunal structure of the assemblages investigated. There were statistical differences in assemblage structure between two separate localities within the rocky patch, despite environmental homogeneity (salinity, water temperature and structure of sea bottom). These differences in assemblage structure were mostly due to differences in dominance of particular species rather than in species composition. Our results show that rocky patches in an otherwise soft sediment habitat provide additional living space for macrofauna leading to an increase in local biodiversity and organismal abundance.
The river Rhine is heavily influenced by human activities and suffers from a series of environmental constraints which hamper
a complete recovery of biodiversity. These constraints comprise intensive navigation and habitat modification by hydraulic
engineering. Improving water quality while these constraints remain in place has led to increased colonization by aquatic
invasive species. This tendency has been accelerated by the construction of canals connecting river basins. Over the last
two centuries, the total surface area of river catchments connected to the river Rhine via inland waterways has been increased
by a factor 21.6. Six principal invasion corridors for aquatic species to the river Rhine are discerned. The extensive network
of inland waterways has allowed macroinvertebrate species from different bio-geographical regions to mix, changing communities,
affecting the food webs and forming new constraints on the recovery of the native biodiversity. From the eighteenth century
onward, in the freshwater sections of the river Rhine, a total of 45 non-indigenous macroinvertebrate species have been recorded.
The average number of invasions per decade shows a sharp increase from <1 to 13species. Currently, the contribution of non-indigenous
species to the total species richness of macroinvertebrates in the river Rhine is 11.3%. The Delta Rhine and Upper Rhine exhibit
higher numbers of non-indigenous species than other river sections, because the sea ports in the Delta Rhine and the Main-Danube
canal function as invasion gateways. Important donor areas are the Ponto-Caspian area and North America (44.4 and 26.7% of
the non-indigenous macroinvertebrate species, respectively). Transport via shipping and dispersal via man made waterways are
the most important dispersal vectors. Intentional and unintentional introductions are highest for the period 1950–1992. The
cumulative number of non-indigenous species in time is significantly correlated with the increase in total surface area of
other river catchments connected to the river Rhine by means of networks of canals. The species richness of non-indigenous
macroinvertebrates is strongly dominated by crustaceans and molluscs. Invasive species often tolerate higher salt content,
temperature, organic pollution and current flow than native species. Spatiotemporal analyses of distribution patterns reveal
that average and maximum dispersal rates of six invasive species vary between 44–112 and 137–461kmyear−1, respectively. Species arriving in upstream sections first show a shorter time lag between colonisation of the Delta and
Upper Rhine than species initially arriving in downstream areas. Temporal analyses of macroinvertebrate assemblages in the
littoral zones indicate that native species are displaced by non-indigenous species. However, established non-indigenous species
are also displaced by more recent mass invaders.
The population of Corophium multisetosum Stock, 1952 in Areão displayed a semiannual, iteroparous life history. Mean longevity was ∼6 mo, with the estimated life
span longer for overwintering individuals born in autumn than for individuals born in spring. Length-frequency data indicated
that the length increment per moult is probably higher in males than females; however females moulted more frequently and
achieved a larger body size. Preliminary growth rates were 100 μm d−1 for juveniles and 19 to 29 μm d−1 for mature females, with the lower values occurring during the winter. It was estimated that under favourable conditions
females may attain reproductive size and mature within 1 mo. Although incubating females were present all year round, recruitment
occurred in spring, almost ceased during the summer, peaked in autumn, and decreased again during the winter. Extreme temperatures
and very low salinities during winter and summer may have deterred breeding, while moderate temperatures (15 to 20 °C) and
salinities > 1 psu in spring and autumn were apparently favourable for reproduction. The unfavourable summer conditions constrained
breeding and synchronised the timing of reproduction. In late-autumn and during the winter, as temperature decreased and brooding
time increased, synchrony was progressively lost. Brood size varied as a function of embryonic developmental stage, size of
incubating females, and season. The life-history pattern and reproductive features of C. multisetosum in Areão are closely related to temperature and salinity; other environmental conditions such as oxygen content of the water
and food availability may also be relevant.
The population ofCorophium multisetosum (L.) from Canal de Mira, Ria de Aveiro, Portugal, was sampled seasonally from December 1985 to September 1986, as part of a larger survey of the benthic invertebrate macrofauna. Its distribution along the channel exposes the species to a range of salinities from freshwater to above 30. A principal components analysis, using the physical and chemical parameters of the sediment as variables and sampling stations as operational taxonomic units, indicated that abundance is negatively correlated with salinity, depth, and the occurrence of sediments rich in particles below 125m and rich in organic matter. Abundance is positively correlated with temperature. The distribution of the species does not seem to be affected by the occurrence of sediment grades between 125 and 1 000m. Paired-choice salinity experiments indicated thatC. multisetosum prefers salinities within the range 2.5 to 10. In multi-choice experiments concerning sediment grade, amphipods did not show any significant preference within the 125 to 500m range, although the 125m grade was chosen less frequently. The influence of temperature on the overall distribution ofC. multisetosum is discussed.
The community structure of the macrobenthic (>1 mm) fauna of an intertidal soft-bottom estuary, the Ra de Foz (Galicia, Northwest Spain) was investigated on 99 occasions during June, September and December 1984 and March 1985. The infaunal data were subjected to classification and ordination techniques. The analyses indicated that sediment characteristics (grain size, percentage silt-clay and organic-matter content) and tidal height are the most important factors governing the distribution and abundance of the intertidal communities. Three faunal assemblages were identified and examined in terms of species dominance, constancy and fidelity. In the clean sands of the outer estuary two main assemblages were distinguished; one, corresponding to the boreal LusitanianTellina community, inhabited the middle and lower tidal levels; the other, typical of a biocoenosis of sands and slightly muddy mediolittoral sands, inhabited the upper tidal level. The third benthic assemblage occupied the muddy sands and mud of the inner estuary and displayed some features in common with theCardium edule-Scrobicularia community described by Thorson.
This study reports on the use of the estuarine amphipod Corophium multisetosum in acute toxicity testing. The species was successfully acclimated to the laboratory and was used in a water-only whole effluent
96 h acute bioassay and in a 10 days whole estuarine sediment test. C. multisetosum response was compared to other species in 96 h bioassays, testing boiling cork effluent and iron filings lixiviates. The
amphipod showed high sensitivity and the results were similar to those obtained with others species namely, the freshwater
cladoceran Daphnia magna, the estuarine amphipod Gammarus chevreuxi and the seawater annelid Sabellaria alveolata. In a 10 days static exposure to natural impacted estuarine sediments, the response of the species was compared to a fertilization
bioassay with the sea-urchin Paracentrotus lividus. Both species indicated the same sediment samples as the most potentially toxic. These samples were collected in sites where
the resident macrofauna benthic community is also the most affected, with strong reduction of the species richness, abundance
and biomass. The results revealed that C. multisetosum presents high potential to be used in routine acute toxicity testing in the estuarine environment.
Based on data, collected in 1980–1990, the intertidal benthic macrofauna of the Schelde and Ems estuaries was compared. The spatial occurrence of the benthic macrofauna along the salinity gradient, including the freshwater tidal area was emphasized. Both estuaries appeared to have a very similar species composition, especially at genus level. The higher number of species observed in the Schelde estuary was probably due to a greater habitat diversity. In both estuaries species diversity decreased with distance upstream. The total density did not vary along the estuarine gradient, whereas biomass is highest in the polyhaline zone.
In both estuaries distinct intertidal benthic communities were observed along the salinity gradient: a marine community in the polyhaline zone, a brackish community in the mesohaline zone, and a third community in the oligohaline and freshwater tidal zones of the estuary. These three communities were very similar between both estuaries. Their main characteristics were discussed together with the occurrence and distribution of the dominant species.
For the Schelde estuary and to a lesser extent also for the Ems estuary, there was evidence that anthropogenic stress had a negative effect on the intertidal macrobenthic communities of the oligohaline/freshwater tidal zone. Only Oligochaeta were dominating, whereas the very euryhaline and/or true limnetic species were missing. In the mesohaline zone, the Schelde estuary was dominated by large numbers of short-living, opportunistic species, whereas in the Ems estuary relatively more stable macrobenthic communities were observed. A comparison with some other European estuaries showed in general similar trends as those observed for the Schelde and Ems estuaries.
During the period 1980–1990 long-term physical, chemical and ecological studies were carried out, to study the changes induced by the building of a storm-surge barrier in the mouth of the Oosterschelde estuary and two large auxiliary compartment dams in the rear ends of the estuary. The storm-surge barrier was constructed in the mouth of Oosterschelde estuary (SW Netherlands) during the period 1979–1986. The barrier allows the tides to enter the estuary freely, and, on the other hand, the barrier guarantees safety for the human population and their properties when a stormflood threatens the area.
Oosterschelde estuary is isolated from the river input, the rear ends of the ecosystem were separated from the estuary by sea-walls and the strongly decreased tidal exchange with the North Sea induced sheltered circumstances. The Oosterschelde changed from a turbid estuary into a tidal bay, and yet primary production responses appear to be robust and resilient, and the biological communities showed only quantitative shifts from the dominance of specific species assemblages to other assemblages. In many cases predicted changes in the structure of the biological communities could not be verified owing to the large natural variability mainly caused by physical factors (e.g. temperature).
The former tidal inlet Lake Veere was turned into a stagnant brackish lake in 1961. Ever since, the system has shown a continuous
degradation. The current study shows the monitoring results for the macrozoobenthic communities and the abiotic conditions
for the period 1990–2008. This includes the first step to remediation, the restoration of the exchange between the tidal marine
Eastern Scheldt and Lake Veere in 2004. A continuous decline in water clearance co-occurring with decreasing macrofauna densities
and richness was observed till 2004. Water quality (e.g., secchi depth, nutrient levels, and oxygen conditions) improved significantly
after the measure at a higher salinity level with less variation. But the macrofauna densities, biomass, and diversity did
not improve yet. First indications of changes in the benthic communities by arrival of new and returning species are however
observed and show that restoration at macrofauna level follows the improved abiotic conditions with a delay of several years.
KeywordsMacrofauna indicators-Benthic communities-Water quality-Restoration-Confinement-Oxygen conditions
The abundance and biomass of Corophium multisetosum Stock, 1952 were determined from benthic corer samples collected monthly over 1 yr in the upper reaches of Canal de Mira
(Ria de Aveiro, Portugal). Both density and biomass over the sampling period were negatively correlated with water temperature
and positively correlated with chlorophyll a concentration in the sediment. C. multisetosum density was significantly negatively correlated with plant biomass and positively correlated with salinity. The nature of
the sediment, favourable environmental conditions, high availability of food and low interspecific competition allowed the
population to reach a maximal density of 200 × 103 individuals m−2 and a maximal biomass (ash-free dry wt, AFDW) of 62 gAFDW m−2. The population was highly productive, especially during the autumn/winter period. Production, estimated by two different
methods (Hynes method: 251 gAFDW m−2 yr−1; Morin–Bourassa method: 308 gDW m−2 yr−1), was much higher than the values reported for other Corophium species. The annual P:B¯ ratio (10) was high, but similar to values reported for Swedish populations of C. volutator and lower than the values estimated from Mediterranean populations of C. insidiosum.
The population of species Corophium urdaibaiense has been studied for a year in the Urdaibai estuary (NE Spain). The new species is characterised by its preference for muddy
sand sediments (15% of mud) and the long body size (with a maximum length of 10.24mm). The maximum abundance occurs in November
(11,600indm−2); it almost disappears at the end of spring. The juveniles represent 79% of the population and the recruitment is concentrated
within the October–December period. The breeding period begins in May, when the temperature is above 15°C, and it ceases in
November, when the temperature is below 15°C. Bivoltinism is probable, taking into account the latitude (43°), temperature
range (12–25°C) and breeding period (May and August–October), but the data are not sufficiently consistent to confirm the
hypothesis. The production ranges from 2.93 to 5.85gm−2year−1, considering one and two generations per year, respectively. Some aspects concerning the food availability, predation and
intraspecific competition could have an influence on the dynamics of the population and are discussed.
Several species of bivalves and procedures have been used to characterize sediment toxicity. Here we report the results of an interlaboratory exercise that included three different laboratories to evaluate the use of the bioassay using the commercial clam Ruditapes philippinarum. Six different dredged sediments were studied using two different endpoints: lethality after two different exposure periods (7 and 14 days) and burrowing activity after 48 h of exposure. The lethal endpoint was only sensitive to characterize samples with high metallic concentration and following the 14-day exposure period. The burrowing activity showed very variable results that evidence the unsuitability of this endpoint for dredged material characterization. According to these results, a new design is recommended for the test using juvenile bivalves if it is to be used to characterize sediment samples on a regulatory context especially if sediments are not affected by metallic contamination.
This and the companion volume describe and illustrate more than 2000 species, form selected protozoans to fishes, found in the coastal waters of the British Isles and north-western Europe. They cover all benthic habitats, from the intertidal zone to approximately 30 metres depth, and also includes representatives of estuarine and supralittoral faunas. Each major animal group is briefly introduced, with notes on the morphology, biology, and ecology of representative species, together with suitable techniques for their collection and study. Short bibliographies list the most important specialist literature for each group. Identification is facilitated by dichotomous keys, first to families, and then to genera or species. Short diagnostic accounts are given for each family and higher taxon; descriptions of all species treated are followed by notes on their ecological and geographical distribution. All species are illustrated by line drawings, with related species grouped together to facilitate comparisons. The two volumes comprise the most comprehensive account of the marine fauna of British and adjacent waters ever produced. It is intended as a bench work for both the professional and amateur marine biologist, as well as for undergraduate and postgraduate students. It is essentially a practical work; taxonomic and synonymic detail is deliberately kept to a minimum, with emphasis given to identification procedures.
The Sado estuary is located on the western coast of Portugal, 40 km south of Lisbon. The present study was undertaken in areas where major dredging activities are planned in relation to harbour development. Investigations of benthic macrofauna assemblages and ecotoxicological effects from sediments collected at the Entrance Channel and the Northern Channel were undertaken as part of a sediment quality assessment prior to a dredging programme. The macrofaunal study was based on the analysis of species richness and abundance. Benthic assemblages were identified through cluster and ordination analysis and compared to baseline data. Species richness and abundance showed spatial gradients very similar to those identified previously. The present data showed a richer amphipod fauna associated with cleaner sediments, marine species typical from coarse clean sediments and fewer species associated with organic enrichment. The ecotoxicology study was based on acute and chronic whole sediment tests with the amphipod Corophium multisetosum and sub-lethal sediment elutriate tests with the sea urchin Paracentrotus lividus. The results showed that the sediments do not present potential toxicity to the organisms tested. These conclusions agree with the results from the macrofauna survey, which illustrated rich, diverse and well-defined gradients. Concerning sediment quality, none of these components impose constraints to dredging. A biodiversity loss resulting from species substitutions may be expected in this area of the estuary.
Aims: In the present study the diet and prey selection of Common Sandpiper Actitis hypoleucos are studied from droppings recollected at an estuary from Northwest Spain, thus extending knowledge of this species biology. Location: The study was carried out from material collected in the river Miño estuary, Pontevedra, Northwest of the Iberian Peninsula. Methods: Information from the analysis of 343 droppings of Common Sandpiper collected during winter (October-February) is examined, tidal variation having taken into account. Prey selection has been studied (prey size and taxonomic selections) contrasting relative abundances from diet and substrate samples. Results: During the winter the diet of this wader species was mainly composed of three marine invertebrates, the amphipod Talitrus saltator (46.9%), the polychaete Nereis diversicolor (39.0%) and the decapod Carcinus maenas (6.3%). Polychaetes and decapods were mainly consumed during low tide periods and sandhoppers consumption corresponded to high tide periods. Contrary to the breeding or migratory seasons, insects were little represented in the diet. Common Sandpiper carried out size and species selection. Although species-specific selection was not remarkable, some grade of selection was detected towards Nereis diversicolor and Talitrus saltator as all other invertebrates were rejected. Carcinus maenas was positively selected, mainly small sized individuals (juveniles). In energetic terms, such selection is conducted towards the consumption of prey with greater profitability. Conclusions: The species shows a feeding behaviour characterized by a diet mainly composed by marine invertebrates reflecting a selection conducted, in energetic terms, towards the consumption of prey with a greater profitability.
Salinity levels in Werra and Weser have reduced by 63% since 1992. Corresponding to that decrease there have been changes in the species communities, phytoplankton dynamics and spatial intensity of primary production. With the changes in primary production, the benthic community has changed. The upstream region of the Weser is dominated by Hydropsychidae in average abundances of 1,000-4,000 Ind. · m-2. The dominant species of the Mittelweser are Dreissena polymorpha, Corbicula fluminalis, Corbicula fluminea and three species of the genus Corophium. Corophium lacustre, Corophium multisetosum and Corophium curvispinum are spread throughout the Mittelweser according to the salinity-gradients. The benthic biocoenosis is dominated by filter-feeders. Other functional components of the foodweb are only rudimentarily developed.
.—Diet and prey selection of Common Sandpiper Actitis hypoleucos during winter. Aims: In the present study the diet and prey selection of Common Sandpiper Actitis hypoleucos are studied from droppings recollected at an estuary from Northwest Spain, thus extending knowledge of this species bio-logy. Location: The study was carried out from material collected in the river Miño estuary, Pontevedra, Northwest of the Iberian Peninsula. Methods: Information from the analysis of 343 droppings of Common Sandpiper collected during winter (Oc-tober-February) is examined, tidal variation having taken into account. Prey selection has been studied (prey size and taxonomic selections) contrasting relative abundances from diet and substrate samples. Results: During the winter the diet of this wader species was mainly composed of three marine invertebrates, the amphipod Talitrus saltator (46.9%), the polychaete Nereis diversicolor (39.0%) and the decapod Carci-nus maenas (6.3%). Polychaetes and decapods were mainly consumed during low tide periods and sandhop-pers consumption corresponded to high tide periods. Contrary to the breeding or migratory seasons, insects were little represented in the diet. Common Sandpiper carried out size and species selection. Although species-specific selection was not remarkable, some grade of selection was detected towards Nereis diversicolor and Talitrus saltator as all other invertebrates were rejected. Carcinus maenas was positively selected, mainly small sized individuals (juveniles). In energetic terms, such selection is conducted towards the consumption of prey with greater profitability. Conclusions: The species shows a feeding behaviour characterized by a diet mainly composed by marine in-vertebrates reflecting a selection conducted, in energetic terms, towards the consumption of prey with a gre-ater profitability. RESUMEN.—Dieta y selección de presas del Andarríos Chico Actitis hypoleucos durante el invierno. Objetivos: En el presente estudio se analiza la dieta y la selección de presas del Andarríos Chico en un es-tuario del Noroeste de la península Ibérica, ampliando así el conocimiento de la biología de esta especie. Localidad: Estuario del río Miño, Pontevedra, Noroeste de la península Ibérica. Métodos: Se examina la información obtenida del análisis de 343 excrementos del Andarríos Chico Actitis hy-poleucos recogidos durante el invierno (octubre-febrero) en un estuario del Noroeste de la península Ibérica. En este análisis se ha tenido en cuenta, además, el estado de marea. También se estudia el grado de selección de sus presas (tanto por tamaños como por grupos taxonómicos) a partir de la comparación de las abundancias de éstas en el sedimento y en la dieta. Resultados: En invierno, la dieta del Andarríos Chico estuvo compuesta en su práctica totalidad por inver-tebrados marinos. Los insectos representaron una fracción muy baja en su alimentación al contrario de lo que ocurre durante la migración o en la época reproductora. Tres invertebrados, el anfípodo Talitrus saltator (46,9%), el poliqueto Nereis diversicolor (39.0%) y el decápodo Carcinus maenas (6,3%), forman el grueso de la dieta de la especie en dicha época del año y sus abundancias en la dieta siguen ese orden de importancia. El poliqueto y el decápodo son presas mayoritarias en el periodo de bajamar y el anfípodo de pleamar. La se-lección del tamaño de las presas en Actitis hypoleucos no parece ser muy marcada ni tampoco parece haber una selección marcada por el tipo de presa. Aunque aparentemente no se hayan obtenido valores significati-vos de selección hacia Nereis diversicolor ni Talitrus saltator existe cierta selectividad ya que el resto de in-vertebrados de las zonas de alimentación son, de alguna forma desdeñados. En cambio sí selecciona positi-vamente a Carcinus maenas, sobretodo ejemplares de pequeño tamaño (juveniles). Conclusiones: La especie muestra un comportamiento alimentario caracterizado por una dieta compuesta en su práctica totalidad por invertebrados marinos reflejando una selección de presas dirigida, en términos energéticos, hacia el consumo de presas que ofrecen un mayor aprovechamiento. Palabras clave: Actitis hypoleucos, Andarríos Chico, dieta, excrementos, invierno, Noroeste de España.
In december 2000 is de Europese Kaderrichtlijn Water (KRW) vastgesteld. Een van de verplichtingen die voortvloeien uit de KRW is het beschrijven van de ecologische referentiesituatie. De referenties vormen het vertrekpunt voor de ecologische doelstelling van natuurlijke watertypen. Er zijn echter nog meerdere stappen nodig om van de referenties te komen tot beleidsdoelstellingen van de actuele waterlichamen in Nederland. De uiteindelijke doelstelling per waterlichaam wordt in 2009 in het Stroomgebiedbeheersplan vastgelegd. De Inleiding (Hoofdstuk 1) gaat in op de uitgangspunten. De Methode (Hoofdstuk 2) geeft een algemene uitwerking van de beoordelingssystematiek per biologisch kwaliteitselement. Vervolgens is per watertype een globale referentiebeschrijving gemaakt die samen met enkele foto?s een beeld geeft van de toestand van het type in nagenoeg onverstoorde omstandigheden. Daarnaast zijn de referentie en de andere vier klassen van de maatlat kwantitatief gemaakt volgens de vereisten van bijlage V van de KRW (Hoofdstuk 3-27). De grens tussen de klasse Goede Ecologische Toestand en Matig is bepalend voor het wel of niet voldoen aan de norm. Ecologie bestaat naast biologie ook uit hydromorfologische- en algemene fysisch-chemische kwaliteitselementen. Conform de vereisten van de richtlijn zijn deze kwaliteitselementen ook kwantitatief ingevuld per watertype. De biologie is daarbij leidend geweest. Voor u ligt de beschrijving van de 9 typen natuurlijke meren, 12 typen natuurlijke rivieren en 4 typen overgangs- en kustwateren
An introduction to the Dreissenidae is presented based on available literature. The origin of the Dreissenoidea mains unclear because a definitive sister group could not be established in spite of extensive morphological and molecular biological studies. It is clear however that the Dreissenoidea belong to the Euheterodonta. More insight was gained with respect to the relationships and phylogeny of the recent species within the family Dreis-senidae. Two clades (sister groups) can be distinguished: Dreissena s. l. and Congeria s. l. (Congeria s. str. and Mytilopsis). Within Dreissena s. l. two sister groups were distinguished, viz. a) Dreissena s. str. and Carinodreis-sena and b) Pontodreissena including Dreissena caputlacus. Three genera of recent Dreissenidae are present in Europe of which the genus Mytilopsis returned after extinction in the Pliocene by a human mediated invasion of Mytilopsis leucophaeata from North America. Most endemic dreissenid species in Europe are locked in tectonic lakes, underground rivers and river and sea basins. However, three recent species were able to extend their areas in Europe and elsewhere, viz. Dreissena polymorpha polymorpha, D. rostriformis bugensis and Mytilopsis leucophaeata. Recent data on the taxonomy, phylogeny, origin and distribution of these species are presented.
The hyperbenthos of the Frisian front, an enriched benthic area of the southern North Sea, and surrounding waters was investigated along two cross-frontal transects in August 1994 and April 1996. A total of 111 species was recorded, mainly peracarid crustaceans and decapods. On average, Calanus spp. (Copepoda), Schistomysis ornata (Mysidacea) and Scopelocheirus hopei (Amphipoda) represented more than 40% of the total density, while S. ornata constituted 30% of the biomass. Community structure differed strongly between the two months, as shown by the species composition and the much lower densities and biomasses in April.
Macroinvertebrate communities on the stones in the Rhine are dominated by the Ponto-Caspian amphipods Chelicorophium curvispinum (since 1987) and Dikerogammarus villosus (since 1995), which have invaded the Rhine through canals connecting the large rivers of Europe. Colonization of bare stones suspended in the water of the Rhine main channel was studied. At the same time the macroinvertebrates drifting in the water layer were sampled. Macroinvertebrate populations on the newly colonized stones were followed for two months (June - August 2002). Bare stones were colonized from the water layer, with D. villosus and C. curvispinum most numerous from the start. Species richness was highest after one month. D. villosus and C. curvispinum continued to dominate the macroinvertebrate community on the stones throughout the experiment, representing 70-95 % of the total number of macroinvertebrates. In the first period week of colonization, especially juveniles of both amphipod species settled on the bare stones. After one week, the number of adults of D. villosus increased. After one month, ovigerous females of D. villosus became abundant on the newly colonized substrate. The numbers of adult C. curvispinum increased after one month and ovigerous females were present after two months. Newly settled populations resembled the amphipod populations present in the water layer, but started to deviate as colonization time increased, indicating that development of populations on stones became increasingly autonomous and less dependent on new colonization by amphipods from the water layer. Ovigerous females of both amphipods were much more abundant on the stones than in the water layer. Juvenile C. curvispinum were smaller on the stones than in the water layer, indicating that the stone substrate is important for reproduction of at least C. curvispinum. Most juveniles of this species first grow to a certain body length on the stones before they start drifting off and swimming in the water layer. C. curvispinum and D. villosus densities were positively correlated in the early stages of colonization, but showed an inverse relationship after longer colonisation time. As both dominant amphipods colonize new stone substrate from the water layer where they drift or swim, they may not depend on extra vectors, such as shipping, for dispersal through the connecting canals and within the river.
The amphipod Corophium volutator has a patchy distribution which has been related to different factors (both physical and biological) at different sites. Experiments in the Wadden Sea, involving manipulation of the densities of the lugworm Arenicola marina and the bivalve Cerastoderma edule showed strong negative effects of these two species on the abundance of C. valutator. This result could explain the distribution pattern of C. valutator found in the Wadden Sea. The question was if this would also be the case in other geographical regions. Therefore, these experiments were repeated under different physical conditions in two shallow and almost non-tidal soft-bottom bays in Gullmarsfjorden on the Swedish west coast. Again, a significant negative density-dependent effect on Corophium was found. This effect was even stronger when A. marina and C. edule occurred together. A. marina and C. edule affected the numbers of the two sexes of C. valutator in a similar way. However, in the treatments with h...
On the tidal flats of the Wadden Sea, a zonation pattern can be found with Corophium volutator and Nereis diversicolor as the dominating species of the upper intertidal zone and Arenicola marina and Cerastoderma edule as the dominating species of the lower zone. As C. volutator can live under a great variety of physical conditions, its restriction to higher areas might result from biotic interactions. This was investigated by field experiments on a tidal flat in the westernmost part of the Wadden Sea. Within large depopulated areas, small plots were recolonized with different densities of N. diversicolor, A. marina, C. edule and Macoma balthica and the subsequent settlement and dynamics of C. volutator were studied. In addition, A. marina and/or C. edule were added to or removed from small plots within a natural benthic community.Neither the presence of M. balthica not that of N. diversicolor significantly affected the abundance of C. volutator. A strongly negative effect was found of C. edule when present in high densities, whereas A. marina negatively affected C. volutator abundance already at relatively low densities. Local removals of A. marina and C. edule from their own zone resulted in increases of Corophium numbers at these locations and local additions of these species within the Corophium zone resulted in decreases of Corophium numbers at these locations. It is suggested that the major species to restrict C. volutator effectively to the upper tidal zone is A. marina.
In the course of identifying them I examined 23 of the 32 species of Corophium, and saw all the literature to which I could find references.
Water works during the 1960s and 1970s changed the northern part of the RhineeMeuse estuary in the south-west of the Netherlands into a freshwater lake, from west to east divided into three basins called the Haringvliet, the Hollands Diep and the Biesbosch. Concurrently water quality parameters (e.g. nutrients and pollutants) changed drastically during the last 50 years. This study combines macrozoobenthic monitoring data from the region from 1960 to 2001 with trends in abiotic parameters to evaluate historic developments of the communities, including den-sities, species numbers and diversity, and assess future developments as a first step to a rehabilitation of the estuary as planned for January 01, 2008. During the 1960s, the macrozoobenthic densities of Oligochaeta and/or Polychaeta dominated communities increased with a gradual decrease of saltwater intrusion and salinity variability. The first years after the basins became stagnant, the species numbers per sample and the Shannon diversity were high due to the coexistence of salt and freshwater species. An increase in nutrient and pollutant loads led to a decrease in the macrozoobenthos densities. As water and sediment quality gradually improved, nowadays the former estuary contains high diversity and high density macrozoobenthic communities, whereas Oligochaeta and/or Polychaeta were dominant in the 1960s, and Bivalvia and Gastropoda were more abundant during the 1970s. Macrozoobenthic communities moved from the east to west with a time-lag, which may primarily be attributed to changing salinities, salinity variances and oxygen levels. Therefore, the current communities of the Haringvliet show similarities with the communities that occurred already during the 1960s in the Biesbosch. This study shows the value of macrozoobenthos monitoring data over longer periods. The possible impact of a new saltwater inlet in the west of the Haringvliet, allowing in the near future saltwater to enter 11.5 km eastward, yet alternated by frequent flushing with freshwater to ascertain that the salt intrusion does not reach further, on the develop-ment of the macrozoobentic communities is discussed.
On the tidal flats in the Dutch Wadden Sea Corophium volutator is a dominant species of the upper intertidal zone; the closely related Corophium arenarium is usually found in the lower zone, but only in low densities (a few hundreds per m2). A survey in the Dutch Wadden Sea showed that this zonation pattern was only present when a muddy sediment was found in the upper zone and a sandy in the lower zone. C. arenarium was restricted to sandy sediments, C. volutator to muddy sediments. Where a sandy sediment was found in the upper intertidal zone, C. arenarium locally occurred in relatively high densities (a few thousands per m2). An aquarium experiment showed that C. arenarium actively avoided muddy sediments.Field experiments were carried out to study the influence of other macrozoobenthic species (known to affect the related C. volutator) on the abundance of C. arenarium. Within large defaunated areas small plots were stocked with different densities of the lugworm Arenicola marina and the cockle Cerastoderma edule. In small plots within a natural benthic community densities of these species were also augmented or (in A. marina) reduced. Strongly negative density-dependent effects of both A. marina and C. edule were found on the abundance of C. arenarium. In the natural situation, its densities showed A. marina to be the most important factor in determining the abundance of C. arenarium. In particular the removal of lugworms caused a strong increase in C. arenarium densities. These results agreed with the distribution of these species along a transect perpendicular to the shore of Schiermonnikoog, where a significant negative correlation was found between the densities of A. marina and C. arenarium. Aquarium experiments showed that the negative effect of cockles and lugworms must be due to migration rather than mortality in C. arenarium.
A few years after it invaded, the amphipod Corophium curvispinum Sars appeared to be the most numerous macroinvertebrate species in the River Rhine. From 1987 to 1991 the densities of this species on the stones of groins in the Lower Rhine at a depth of 0.5 m increased from 2 to 200000 specimens per m2. In the Lower Rhine and its branches the densities of C. curvispinum increased with increasing current velocities and with increasing water depths. So far, a maximum population density of 750000 specimens per m2 has been found in the Lower Rhine, which is many times the densities recorded elsewhere. Population parameters, densities and distribution of C. curvispinum were studied in the Lower Rhine and its branches, using artificial substrates and sampling stones from groins. The success of this immigrant is related to its competitive strategy, which shows several aspects of a r-strategy. In addition, the heavily eutrophicated Lower Rhine provides abundant food (phytoplankton, suspended organic matter) for this opportunistic filter-feeder. The increased salinity and water temperatures in the Lower Rhine resulting from industrial discharges have contributed to the current success of this southern species originating in brackish waters. The very high densities of C. curvispinum might have an enormous impact on the river ecosystem by changing food webs.
The macroinvertebrate community of the harbour of Ghent was studied by analysing 135 samples taken at different sampling locations
from 1990 until 2008. The results showed that the current Crustacea and Mollusca communities are mainly represented, in terms
of abundances, by alien species. In total, seven alien and four indigenous crustacean species were found. Mollusc diversity
was higher, with a total of 14 species, four of which were alien. Macroinvertebrate diversity was very low at the beginning
of the 1990s, but increased due to the improvement of the chemical water quality achieved by sanitation and stricter environmental
laws. This is reflected by the dissolved oxygen concentration, which increased from an average of 2mg/l to an average of
9mg/l, allowing more sensitive species to establish. Since 1993, the number of alien taxa has augmented, whereas the number
of native taxa has remained stable. The improvement of the chemical water quality and the simultaneous increase in total number
of species were also reflected in an increase of the Multimetric Macroinvertebrate Index Flanders, which is used to assess
the ecological water quality in Flanders. Due to intensive international boat traffic and the low species diversity, the harbour
of Ghent is highly vulnerable for invasions. Stronger regulations and a better understanding about the contribution of shipping,
shortcuts via artificial water ways, habitat degradation and environmental pollution are required to reduce the further spread
of alien species.
KeywordsAlien species–Macrocrustaceans–Molluscs–Water quality
The amphipod fauna of the delta of the rivers Rhine, Meuse and Scheldt was re-surveyed 30 years after the detailed inventory ofden hartog (1963; 1964). During these 30 years enormous changes have taken place in the morphology and hydrology of this estuarine system. Many habitats were destructed because of the damming of several sea arms. Tidal influence disappeared from a large part of the area or was reduced in other parts. Nearly all indigenous amphipods of the area have suffered severely under these changes. The only species to profit were the recently introducedGammarus tigrinus andCorophium curvispinum. The main causes for the sharp decline of the amphipod fauna are changes in salinity, tidal movements and dike construction.
The use of benthic assemblages to assess ecological quality of estuarine environments is a major tool for the implementation
of the Water Framework Directive (2000/60/CE) for European aquatic ecosystems. Benthic communities show spatially heterogeneous
distributions and experience seasonal variations due to both natural and anthropogenic stresses. The major goal of this study
was to quantify the relationships between environmental gradients and the spatial and temporal patterns of the benthic communities
along a Portuguese estuary. Seasonal and spatial variations relating macrobenthic communities and measures of water and sediment
quality along the northern branch of the Mondego River estuary were examined at seven sampling stations from July 2000 to
June 2001. Cluster analysis of biological data indicated three major groups of communities based on spatial distribution patterns:
(1) a lower sector with stronger marine influence and dominated by Streblospio shrubsolii and Cerastoderma glaucum; (2) a middle sector with dominance of S. shrubsolii and Corophium multisetosum; (3) and an upper sector where C. multisetosum dominates a community characterized by a lower number of species. Canonical correspondence analyses of biological and environmental
data determined a major salinity gradient influencing benthic communities. Seasonal changes of benthic communities were mainly
determined by freshwater input and salinity changes that imposed a strong decrease in densities and number of species during
winter, followed by a recovery during spring. Benthic ecological structure and contaminant levels indicated that the Mondego
northern branch is moderately disturbed, although opportunistic species dominated the benthic community, suggesting that natural
and anthopogenic sources of stress may be acting together. The Mondego River estuary, a poikilohaline-type estuary, characterized
by strong seasonal changes in water flow and salinity, cannot be consistently stratified into salinity regions based upon
the Venice classification system. Biotic communities, exemplified here by the benthic communities, are seasonally displaced,
compared to a homiohaline-type estuary where the Venice system can be applied without modification. Future identification
of reference conditions and design of monitoring programs cannot be accomplished without understanding how interactions between
biotic and physico-chemical dynamics differ between homiohaline and poikilohaline estuaries. Results obtained in this study
could be used to assist future assessments in other Portuguese estuaries.
Significant anthropogenic pressure in the Dutch part of the River Rhine is present from the 12th century. River engineering
and water pollution were the main stress factors for flora and fauna. From the middle of the 20th century measures were taken
to reduce water pollution. Recently, from 1987 onwards, these activities were put into a wider context of ecological river
rehabilitation. Effects of improvements on fish and macroinvertebrates in the main distributaries in the Rhine delta are reviewed.
The conclusions are that (a) most of the alterations in the Rhine delta are irreversible due to hard socio-economic boundary
conditions (e.g. safety, navigation); (b) chances for the development of riverine biotopes have therefore to be found in the
forelands and not in the main channels of the Rhine delta; (c) further reduction of pollutants, especially thermal pollution,
is needed to help original species to colonise the Rhine delta again; (d) non-indigenous species clearly leave a mark on recolonisation
possibilities of original species.
Macroinvertebrates were studied during the first five years after closure and freshening of the lake system Volkerak-Zoom, two lakes interconnected by a channel. Before embankment, in 1987, these lakes were part of the tidal eastern Scheldt estuary in the south-western part of the Netherlands. Four months after embankment, the first freshwater species were found. In general, the colonization process followed the same pattern as was reported for newly created reservoirs. In Lake Volkerak-Zoom differences in colonization time were observed between distinguished depth zones. Within the chironomid assemblages, dominance of Chironomus muratensis was followed by a dominance of Procladius, Glyptotendipes and Cladotanytarsus. The succession was related to changes in phytoplankton concentrations. Although in 1991 changes in macrofauna composition were less pronounced as compared to previous years, succession was still going on.
In this paper, a marine Biotic Index (BI) for soft-bottom benthos of European estuarine and coastal environments is proposed. This is derived from the proportions of individual abundance in five ecological groups, which are related to the degree of sensitivity/tolerance to an environmental stress gradient. The main difference with previously published indices is the use of a simple formula that produces a continuous Biotic Coefficient (BC) – which makes it more suitable for statistical analysis, in opposition with previous discreet biotic indices – not affected by subjectivity. Relationships between this coefficient and a complementary BI with several environmental variables are discussed. Finally, a validation of the proposed index is made with data from systems affected by recent human disturbances, showing that different anthropogenic changes in the environment can be detected through the use of this BI.