Cost/benefit analysis of a benthic monitoring programme of organic benthic enrichment using different sampling and analysis methods

To investigate the combined effects of decreasing taxonomic resolution (i.e. species, family, phylum), the use of different mesh-size (1.0 mm and 0.5 mm) and the type of samplers used (van Veen vs. corers taken by divers) on the quality of data obtained, a comparative study was undertaken with the overall aim of identifying cost efficient methods for routinely monitoring the ecological change caused by Mediterranean fish farming. The results clearly showed that information loss was relatively low as data were aggregated at higher taxonomic levels, particularly up to the level of family or even order. It was also found that the extra information gained by sieving samples through a 0.5 mm sieve did not improve the ability to distinguish the potentially impacted sites from the control stations. Finally, it was found that a relatively large proportion of the available information concerning the community structure such as abundance, biomass or diversity is lost when sampling is carried out with corers. A cost/benefit ratio analysis for the two sampling and the two sieving methods showed minimal values for the van Veen samples (for both sieve fractions) at the family level, indicating that analysis at this level gives the best balance between precision of the results and decrease in taxonomic effort. However, if the time needed to sort the samples is included in the analysis, then samples taken with corers using a 0.5 mm sieve and identified to families seems like a good compromise between precision and cost.     

Multivariate Analysis of Species Distribution: A Survey on Occurence of Mangrove Molluscs in the Bonny and New Calabar Rivers of the Niger Delta Multivariate Analyse von Verbreitungsmustern: Ein Überblick über das Vorkommen von Mangroven-Mollusken im Bonny River und New Calabar River des Niger-Deltas

Studies on distribution and habitats of mangrove molluscs of the Bonny and New Calabar rivers (Niger Delta) were made at ten shore stations from the river mouth to the tidal fresh water zone. Forty-three species were collected and thirty-nine were identified. Investigations into tidal zonation patterns showed that molluscs inhabited the high, mid and low intertidal stretches of the shore. In the tidal fresh water and low-salinity brackish water zone, the low intertidal is poor in molluscs. Many species have restricted salinity ranges occuring either in the high or low salinity limits. The collected data on occurence of species were analyzed by different methods from multivariate data analysis, namely cluster analysis, principal component analysis and partial least squares. These allowed to visualize structures among mollusc species and stations according to distribution patterns and to estimate the degree of relation between these patterns and salinity.     

Constraints on spatial variability in soft-sediment communities affected by contamination from an Antarctic waste disposal site

A small-scale (<500 m length) transect-based survey was conducted in December 1998 to examine the spatial distribution of soft-sediment communities and of concentrations of heavy metals and hydrocarbons in sediments in Brown Bay, adjacent to an abandoned waste dump, at Casey Station, Antarctica. Samples were taken along three transects at increasing distances (nine stations) from the shore-line waste dump. A gradient of contamination was detected, but concentrations of contaminants were very variable with "hotspots" or high levels of contaminants at some stations. Multivariate analysis revealed that the distribution of soft-sediment communities was distinctly different between the inner, middle and outer stations. Abundances of most taxa were very variable with few patterns apparent, but some fauna displayed an abundance gradient from the inner to the outer part of the bay. Many taxa had maximum abundances at outer stations and minimum at inner stations. Multivariate correlations between environmental variables and soft-sediment communities indicated that combinations of some metals (Cd, Cu, Sn, Pb) and grain size (mainly finer fractions, fine sands and coarse silts) were the variables that best "matched" the community patterns within Brown Bay. This study indicated that there were significant correlations between the presence of contaminants and the distribution and composition of soft-sediment communities over very small spatial scales.     

The use of time-series data in the assessment of macrobenthic community change after the cessation of sewage-sludge disposal in Liverpool Bay (UK)

Sewage sludge was disposed of in Liverpool Bay for over 100 years. Annual amounts increased from 0.5 million tonnes per annum in 1900 to approximately 2 million tonnes per annum by 1995. Macrofauna and a suite of environmental variables were collected at a station adjacent to, and a reference station distant from, the disposal site over 13 years, spanning a pre- (1990-1998) and post- (1999-2003) cessation period. Univariate and multivariate analyses of the time-series data showed significant community differences between reference and disposal site stations and multivariate analyses revealed station-specific community development post-disposal. Temporal variability of communities collected at the disposal station post-cessation was higher than during years of disposal, when temporally stable dominance patterns of disturbance-tolerant species had established. Alterations of community structure post-disturbance reflected successional changes possibly driven by facilitation. Subtle faunistic changes at the Liverpool Bay disposal site indicate that the near-field effects of the disposal of sewage sludge were small and therefore could be considered environmentally acceptable.     

On the use of meiofauna in ecological monitoring: Who needs taxonomy?

Taxonomic problems have hindered the widespread use of meiobenthos for the purpose of pollution monitoring despite its potential usefulness. The question whether it is necessary to go down to species level in order to distinguish assemblages and stations was studied using data on meiofauna densities available from a GEEP-workshop held in Norway, August 1986.

Using the complete species list of harpacticoid copepod and nematode species, the six stations could be clearly separated by different multivariate techniques (TWINSPAN, DCA, MDS, Clustering). The abundance data of the genera, the families and even the orders (in the case of nematodes) still allowed a more or less clear separation of the stations, although their relative relationships were sometimes distorted. Thus, from a practical point of view, it may be sufficient to identify the animals to genus or family level.

It is proven that this result is not due to ecological similarities between congeneric or confamiliar species. The species groups typifying the stations in the TWINSPAN analysis did not contain more confamiliar species pairs than expected from random sorting. Randomly assembled ‘families’ allowed a separation of the stations as clear as that based on taxonomic groups.

We conclude that the information contained in species abundances was preserved, at least partially, when the species are grouped, even at random. The grouping in higher taxonomic categories was as good as any, and more convenient than all the others. However, within the (limited) range of habitats studied, ecological adaptation is achieved nearly exclusively on the species level.     

Decline of the Jakarta Bay molluscan fauna linked to human impact

In 1937/38 representative mollusc collections were made in Jakarta Bay (West Java, Indonesia). New data from here and the adjacent offshore Thousand Islands archipelago (Kepulauan Seribu) became available in 2005. Although collecting efforts and sampling methods differed, a comparison of the molluscan fauna of Jakarta Bay between 1937/38 and 2005 reveals a distinct deterioration. From 1937 to 2005, Jakarta Bay received increasing amounts of sewage from the greater Jakarta area, as well as increased sediment input from the deforested West Java hinterland. Predatory gastropods and numerous mollusc species associated with carbonate (reef) substrate have vanished from Jakarta Bay, among which many edible species.     

Relationship of metal content and bioavailability with benthic macrofauna in Camamu Bay (Bahia, Brazil)

Camamu Bay (Bahia, Brazil) is an Environmental Protected Area with mangroves of economic and ecological importance. The objective of this study was to elucidate, through the distribution of the benthic macrofauna and its relationships with trace metals and bioavailabilty, if the current quality of the mangrove sediments of Camamu Bay is acceptable for the protection of aquatic life. Seven sampling stations were selected as representative of the meso-littoral region of Camamu Bay. It was found 581 macrobenthic organisms distributed in 38 species. The highest values of metals occurred at stations located in areas that influenced by barite extraction, while the lowest concentrations were found in areas with relatively lower anthropogenic influence. Analysis of acid volatile sulphide and simultaneously extracted metals showed the occurrence of the ratio SEM/AVS >1, indicative of possible bioavailability of metals, at only one station. The results suggested that Camamu Bay is a nearly pristine area.     

The distribution of trace metals in Florida Bay sediments

The distribution of trace metals based on surface sediments collected at 40 stations across Florida Bay was done in June, November and February 2000-2001. Concentrations of Sc, V, Ba, Cd, Cr, Co, Cu, Pb, Mn, Ni, Zn, Al and Mg were determined by ICP-MS, and the total Fe was determined by spectrophotometry. Organic carbon (OC), nitrogen (N), and calcium carbonate (CaCO3) were also measured. Eleven of 13 metals showed a similar distribution pattern for the various months studied. Maximum concentrations of metals were lower than those found in most estuarine systems and were concentrated in the north-central and western zones of the Bay. The Mn and Fe concentrations, unlike the other metals, gradually decreased from north (Everglades) to south (Florida Keys). Some metals (Ni, Zn, Cu, Cr, Pb and Ba) associated with petroleum use showed high concentrations at stations near the Tavernier marina. Florida Bay sediments are predominately CaCO3 (65.9-92.5%). The greatest value for OC (5.5%) and the lowest value of CaCO3 (65.9%) were found in the western zone. Trace metal distribution patterns are similar to the OC and N in the sediments. There was a strong correlation between most metals (V>Cu>Ni>Cr>Al>Co>Ba>Zn>Pb>Mg) and the percentage of OC. The maximum C/N values (9-12) were observed at the stations with the highest OC, where dense colonies of seagrass are found and most of the metals are concentrated. All metals except Mg, Mn and Co showed a strong correlation with Al and the fine fraction of the sediments (aluminosilicates) associated with continental input and river runoff.     

Long-term trends in the macrobenthos and water quality of the lower Chesapeake Bay (1985–1991)

Long-term trends in macrobenthic communities of the lower Chesapeake Bay, USA, were examined using data collected quarterly (March, June, September and December) from 1985 to 1991 at 16 stations along a salinity gradient from tidal freshwater regions of the major tributaries (James, York and Rappahannock rivers) to the polyhaline region of the main-stem of Chesapeake Bay. A non-parametric trend analysis procedure was applied to five parameters characterizing macrobenthic community structure: community biomass, species richness, abundance of individuals, proportion of biomass composed of opportunistic species (opportunistic biomass composition) and proportion of biomass composed of equilibrium species (equilibrium biomass composition). For the parameters tested 36 trends were detected. For community biomass, five trends were significant; all had positive slopes and occurred in the James and York rivers. For species richness, six trends were significant; all had positive slopes with three trends in the James River, two trends in the York River and one trend in the main-stem of Chesapeake Bay. For abundance of individuals, 17 trends were detected; all abundance trends were seasonally dependent, had positive slopes and occurred at 12 of the 16 stations. For opportunistic biomass composition, four trends were significant; all had positive slopes with one trend in the lower Rappahannock River and three trends in the main-stem of Chesapeake Bay. For equilibrium biomass composition four trends were significant; two trends had positive slopes (one in the James River and one in the York River) and two trends had negative slopes (one in the Rappahannock River and one in the main-stem of Chesapeake Bay). Trends in the James and York rivers were considered to indicate improving conditions for the benthos, while trends in the lower Rappahannock River and the main-stem of the Chesapeake Bay were considered to indicate deteriorating conditions. Deteriorating conditions for the benthos were associated with regions exposed to summer, low dissolved oxygen events. The trends in the indicators of benthic biological community health were inferentially related to trends observed in water quality conditions in the tributaries and main-stem of Chesapeake Bay. All major water quality and biotic trends appeared to correspond in an ecologically meaningful manner.     

The long-term dynamics of crustacean communities in Lake Constance (Obersee, 1962–1986)

The long-term development of crustacean associations in the Obersee of Lake Constance was studied at one central station from 1962 to 1986. In a simultaneously managed program with four additional stations from the eastern part (Bregenz Bay) to the western überlinger See mainly the differences in horizontal distribution were focussed. It was one aim of these investigations, to get an idea or an indication of a connexion between the recently observed eutrophication of the Obersee, and its crustacean communities. Due to the immigration of several species (cyclopids) or genotypes (Daphnia), the communities had changed in genetical structures, in reproduction rates and in predation or grazing impact. Dependent on the specific annual cycles, there resulted an extermination (Heterocope, Diaphanosoma), or a long-term decrease in annual means (Mesocyclops, Cyclops abyssorum) of the “old-settled” species. A general tendency was seen in an increase of annual averages until the middle of the seventies, and a following decrease of population density of most of the species. The horizontal differences in the species associations were remarkable. The Bregenz Bay showed an own aspect in its crustacean community with high total numbers and in earlier spring development. Most of the newcomers were concentrated in the eastern part of the lake.     

太湖贡湖湾水生植被分布现状(2012年)

贡湖湾是无锡和苏州两市的重要水源地,随着近些年太湖水质的急速恶化,贡湖湾蓝藻暴发现象日益严重,危及饮水安全.为提供贡湖湾水资源管理的理论依据,于2012年开展贡湖湾水生植被野外调查.对8个断面进行为期5天的调查,结果表明:(1)共记录贡湖湾水生植物20科27属34种,单子叶植物和沉水植物分别为优势分类群和生态型;(2)贡湖湾水生植被分布区面积占总水域面积的45.35%,为典型半草型湖泊;(3)共有8种水生植物群落分布,其中马来眼子菜群落分布区面积和生物量最大;(4)贡湖湾水生植被总体表现出北部无水生植被分布,东部生物量高、群落及物种组成复杂,其他区域生物量小、群落组成单一的分布格局.水质恶化和插网捕鱼对贡湖湾水生植被分布现状存在影响,过度清淤可能是造成北部水域裸露的原因.结合贡湖湾水生植被分布现状分析结果,建议在贡湖湾水生植被管理中要开展北部裸水区植被修复,促进湾口区域马来眼子菜群落生长,加强对"引江济太"工程上游来水和贡湖湾水质的监测,并注重外来入侵植物尤其是水盾草群落的监测.     

A cross-continental comparison of stream invertebrate community assembly to assess convergence in forested headwater streams

We studied two forested, headwater streams to compare patterns of invertebrate community structure and consequences for ecosystem functioning in two temperate locations, Galicia (NW Spain) and Vancouver (SW Canada). The two sites were selected due to the similar dominance of congeneric invertebrate species, as well as similarity in their hydromorphological and physico-chemical characteristics. Field experiments tested for similarities and dissimilarities in the invertebrate community assembly in leaf packs in streams. Our results indicated that alder leaves always decomposed faster than eucalyptus leaves, from threefold higher in Galicia to tenfold in Vancouver. At the species level, the biogeographic factor was the main source of variation on invertebrate assemblages (84.9 %), but this percentage quickly decreased at higher levels of taxonomic resolution, i.e. family. Moreover, there was a strong leaf species influence in both sites. There were more invertebrates colonizing leaves (per unit mass) in Vancouver than in Galicia (fourfold on average), though alder leaves seemed to be always the preferred resource (5.5-fold higher density on average). Regardless, a similar trophic structure was found between sites and leaf species. Brillia spp. and Corynoneura spp., a shredder and a collector-gatherer, respectively, seemed to be the most important species and showed similar colonization patterns in both sites with potential to strongly influence the leaf processing and nutrient cycling in these ecosystems. Even though our results are limited to the similarity found between only two sites, results from other studies, where the same species have been found coexisting during leaf pack processing, reinforces our results that common rules and mechanisms determine patterns of key ecological processes on a biogeographical scale.     

EROD activity, serum SDH and PAH biliary metabolites in sand flathead (Platycephalus bassensis) collected in Port Phillip Bay, Australia

In order to evaluate the health status of fish inhabiting Port Phillip Bay, Australia, southern sand flathead (Platycephalus hassensis, N = 133) were collected at six stations throughout the Bay. Fish had a similar serum sorbitol dehydrogenase (SDH) activity level (p = 0.12), indicating that they were not experiencing hepatocellular injuries. Ethoxyresorufin-O-deethylase (EROD) activity was generally lower in the non-urbanized and non-industrialized southern part of the Bay. The highest EROD activity was observed in Hobson Bay, the closest station from Melbourne city. Naphthalene-type biliary metabolites were also highest in Hobson Bay with intermediate levels found in Corio Bay where refineries are present. An opposite trend was observed with the pyrene-type bile metabolites, the highest levels being observed in Corio Bay while intermediate levels were found in Hobson Bay. The ratio of naphthalene-type to benzo(a)pyrene (B(a)P)-type metabolites indicate that relatively to other sites sampled in Port Phillip Bay, Corio Bay is subjected to enriched petroleum hydrocarbons of pyrolytic origin. Temporal trends indicate that the availability of xenobiotics to fish remained unchanged over the 1990s.     

Underwater noise pollution in a coastal tropical environment

Underwater noise pollution has become a major concern in marine habitats. Guanabara Bay, southeastern Brazil, is an impacted area of economic importance with constant vessel traffic. One hundred acoustic recording sessions took place over ten locations. Sound sources operating within 1 km radius of each location were quantified during recordings. The highest mean sound pressure level near the surface was 111.56 ± 9.0 dB re 1 μPa at the frequency band of 187 Hz. Above 15 kHz, the highest mean sound pressure level was 76.21 ± 8.3 dB re 1 μPa at the frequency 15.89 kHz. Noise levels correlated with number of operating vessels and vessel traffic composition influenced noise profiles. Shipping locations had the highest noise levels, while small vessels locations had the lowest noise levels. Guanabara Bay showed noise pollution similar to that of other impacted coastal regions, which is related to shipping and vessel traffic.     

Comparing efficacy of different taxonomic resolutions and surrogates in detecting changes in soft bottom assemblages due to coastal defence structures

Sandy shores on the West coast of the North Adriatic Sea are extensively protected by different types of defence structures to prevent coastal erosion. Coastal defence schemes modify the hydrodynamic regime, the sediment structure and composition thus affecting the benthic assemblages. This study examines the effectiveness in detecting changes in soft bottom assemblages caused by coastal defence structures by using different levels of taxonomic resolution, polychaetes and/or bivalves as surrogates and different data transformations. A synoptic analyses of three datasets of subtidal benthic macrofauna used in studies aimed at assessing the impact of breakwaters along the North Adriatic coast has been done. Analyses of similarities and correlations between distance matrices were done using matrices with different levels of taxonomic resolution, and with polychaetes or bivalves data alone. Lentidium mediterraneum was the most abundant species in all datasets. Its abundance was not consistently related to the presence of defence structures. Moreover, distribution patterns of L. mediterraneum were masking the structure of the whole macrofaunal assemblages. Removal of L. mediterraneum from the datasets allowed the detection of changes in benthic assemblages due to coastal defences. Analyses on different levels of taxonomic resolution showed that the level of family maintained sufficient information to detect the impacts of coastal defence structures on benthic assemblages. Moreover, the outcomes depended on the transformation used. Patterns of distribution of bivalves, used as surrogates, showed low correlations with the patterns of the total macrofaunal species assemblages. Patterns of polychaetes, if identified to the species or genus level showed higher correlations with the whole dataset. However, the identification of polychaetes to species and genus level is as costly as the identification of all macrobenthic taxa at family level.This study provided additional evidences that taxonomic sufficiency is a useful tool in environmental monitoring, also in investigations on the impacts of coastal defence structures on subtidal macrofauna. The use of coarser taxonomic level, being time-efficient, would allow improving sampling designs of monitoring programs by increasing replication in space and time and by allowing long term monitoring studies.     

Status of Macrobenthic Community and Its Relationships to Trace Metals and Natural Sediment Characteristics

Laizhou Bay, located in the northwest of Shandong Peninsula, has complex transitional environments between terrestrial and marine ecosystems. In the present study, a total of 122, 131, and 139 species were collected in spring, summer, and autumn 2011, respectively. Species constitutions of macrobenthos were grouped into four phyla, of which annelida were the most abundant phylum, the average biomass proportion of echinodermata was the lowest, and the proportion of important species for mollusca was the highest. The structure of the macrobenthic community showed significant differences between sites, and greater divergence was observed between the third site (S03) and other stations. The ABC plots showed that the biomass curve lay below the abundance curve, and the W‐statistic value was negative. The result of the BOPA index showed that two stations had moderate ecological status in spring and that there were two heavily polluted sites and one moderately polluted site in summer. The BIO‐ENV analyses indicated that the grain‐size fractions together with trace metals (Hg, Pb, Zn, Cu, and Cr) could be considered as the major environmental variables influencing the macrobenthic patterns. The results together demonstrated that the macrobenthic communities in Laizhou Bay were negatively affected, perhaps by the tremendous impact of heavy metals in the sediments.     

Environmental variabilities and the distribution of octocorals and black corals in Hong Kong

A recent comprehensive survey covering 125 sites in Hong Kong waters recorded 29 soft coral species in 14 genera, 38 species of gorgonians in 19 genera and six species of black corals in two genera. Environmental variabilities based on water quality data collected by Hong Kong Environmental Protection Department were analyzed using multivariate statistics to find variables that are significantly correlated with coral distribution patterns. Eleven water quality zones with similar environmental variabilities were recognized, which could further be classified into five groups, namely Inner Bay, Outer Bay, Eastern, Western and Southern waters. LINKTREE analysis provided an overall trend indicating the importance of salinity, sediment and nutrient loadings in affecting octocoral and black coral distribution from west to east of Hong Kong waters, and from inner to outer bays. Furthermore, water turbidity and wave exposure could also affect the coral distribution patterns from north, northeast to southern waters.     

Temporal and spatial trends of total petroleum hydrocarbons in the seawater of Bohai Bay, China from 1996 to 2005

The temporal and spatial distribution of total petroleum hydrocarbons (TPH) in the seawater of Tianjin Bohai Bay during 1996-2005 was investigated for the first time. TPH concentrations in 480 seawater samples collected from 16 stations during a 10-year span were quantified by ultra-violet fluorescence spectroscopy. Petroleum hydrocarbons were ubiquitous in the seawater, and their concentrations were highly variable, ranging from 23.7 to 508 μg L⁻¹. TPH concentrations in the seawater varied with seasons, showing a decreasing order of winter > spring > summer. Over the 10-year period, TPH at all stations steadily decreased. The highest values obtained were at stations near the port areas and Dagu outfall where shipping activities and land-based waste water discharges were the major sources of pollution. Our results provided the background information on the extent of TPH contamination in the seawater and highlighted the need to further control TPH pollution in Tianjin Bohai Bay.     

Patterns of asynchrony for phytoplankton fluctuations from reservoir mainstream to a tributary bay in a giant dendritic reservoir (Three Gorges Reservoir, China)

Seasonal fluctuations of phytoplankton have often been regarded as one of the important cyclic events in aquatic ecosystems, and have even been emphasized as an important sign of regional climatic variability in limnology. However, few attempts have been made to examine synchrony for phytoplankton fluctuations among different habitats in a single reservoir system. The present study employed Spearman rank correlation analysis and the Mantel test to assess levels of synchrony for phytoplankton abundance and taxonomic composition from reservoir mainstream to a tributary bay (Xiangxi Bay) in a giant dendritic reservoir, China (Three Gorges Reservoir, TGR). At the selected scale, asynchronous patterns of phytoplankton were found when looking at total abundance and taxonomic composition, suggesting that regional drivers were not strong enough to synchronize phytoplankton fluctuations, and local regulators were predominant. As a riverine system, the mainstream of TGR had high levels of algal synchrony, while asynchronous patterns of phytoplankton were detected within Xiangxi Bay, which is characterized as a lacustrine system. The present study further confirmed that external hydrological disturbances strongly homogenize habitat conditions and synchronize phytoplankton fluctuations within the mainstream, while spatial divergence of phytoplankton succession depend on local habitat conditions within Xiangxi Bay. Moreover, low synchrony of phytoplankton between the mainstream and Xiangxi Bay is probably caused by spatial divergence of phytoplankton succession within Xiangxi Bay and the lack of succession in the rapidly flushed mainstream. Independently of these mechanisms possibly explaining phytoplankton fluctuations, the present study has also an applied perspective to the improvement of a long-term observation program in which phytoplankton trends at the mainstream scale could be compiled from the data set in a single site, while a set of sampling sites should be required at the Xiangxi Bay scale.