The space–time dynamic of phytoplankton diversity and succession was investigated during the wane of a Phaeocystis globosa spring bloom in four distinct hydrological sub-systems of the eastern English Channel. Nutrients, chlorophyll-a concentrations, and phytoplankton composition, standing stocks, size spectra and diversity were monitored during three key periods in 2003: late spring, early summer and summer. Two consecutive diatom assemblages were observed, respectively dominated by: (i) small colonial species (<100 μm; Melosira sp., Diploneis sp. and Navicula transitans) in April; and (ii) large fine-walled cells (>200 μm; Guinardia striata and Rhizosolenia imbricata) in May and July. This shift in diatom composition appeared to be related to the potentially limitating silicic acid in early summer. Specific phytoplankton assemblages identified in distinct water masses have evolved from a mature/senescent community towards a relatively homogeneous aestival structure of dominant species that might have been triggered by the wane of the P. globosa bloom. Our results also identified a strong heterogeneity in the distribution of secondary species between distinct water masses during the summer period, suggesting that the magnitude of the observed patterns was intrinsically related to the hydrological properties prevailing in each sub-system. The identification of distinct temporal patterns in phytoplankton species diversity and succession following the wane of a spring bloom at relatively small spatial scales (i.e. <10 km) is discussed in the framework of P. globosa blooms in particular and phytoplankton blooms in general and is suggested to have potentially strong consequences on food web dynamics and the carbon cycle in coastal ecosystems.

Despite a recent revision of the dinoflagellates of the order Dinophysiales on Mexican coasts and a checklist of dinoflagellates from the Mexican Pacific, many records still need to be confirmed, for there are very few reliable illustrations and/or descriptions. In this paper, species composition and distribution of dinoflagellates belonging to the Dinophysiales, the product of the analysis of net phytoplankton material collected from coasts of the tropical Mexican Pacific (Jalisco to Chiapas) are presented. The material has been studied using light microscopy, although a few species were also studied by scanning electron microscopy (SEM). Forty-one species from five genera were identified, with two new records annotated for the Mexican Pacific: Amphisolenia thrinax and Metaphalacroma skogsbergii, and two new species of the genus Amphisolenia, Amphisolenia fusiformis sp. nov. and Amphisolenia michoacana sp. nov. Illustrations, dimensions and distribution data are provided for each species, and descriptions of the new species are also given. Amphisolenia palmata, A. rectangulata, A. truncata, Dinophysis apicata, D. hindmarchii, Histioneis biremis, H. crateriformis, H. pulchra, Ornithocercus cristatus, O. heteroporoides and O. orbiculatus are illustrated for the first time in the waters of the Mexican Pacific. The number of species found in this study is relatively low. The species Dinophysis norvegica and D. sacculus, reported in previous papers, do not seem to occur in Mexican waters, as their distribution is rather limited to the Mediterranean Sea and the North Atlantic, respectively. Finally, the identity of certain species of Dinophysis and the nature of the new species described here are discussed.

In recent years there has been an increase in community-based monitoring programmes developed and implemented worldwide. This paper describes how the data collected from such a programme could be integrated into a Geographic Information System (GIS) to create temperate subtidal marine habitat maps. A differential Global Positioning System was utilized to accurately record the location of the trained community-based SCUBA diver data. These georeferenced data sets were then used to classify benthic habitats using an aerial photograph and digitizing techniques. This study demonstrated that trained community-based volunteers can collect data that can be utilized within a GIS to create reliable and cost-effective maps of shallow temperate subtidal rocky reef systems.

The factors potentially leading to the development of periodic hypoxia were investigated based on field studies performed over a series of two years between November, 1997 and November, 1999. This was attempted by investigating both hard and soft seafloor. Descriptive and predictive models were developed that incorporated physical, chemical and biological data derived from the present study and previous work and were used to anticipate future possible crashes of the faunal communities due to hypoxia/anoxia. It was concluded that periodic hypoxia at Ardbear is a natural event caused by several factors to varying degrees. The results of the present study indicate that the major controlling factors for oxygen depletion are the shallow depth of the system, coupled with the development of thermal stratification during periods of calm ambient meteorological conditions of the warmer summer months. In addition, a soft, muddy bottom and highly productive plankton blooms exacerbate conditions in a system already predisposed to hypoxia.

The study area for this work includes all the southern edge of the Bay of Biscay, from the north-west Iberian Peninsula to the southern half of the French shelf. The principal aim of this article is to provide a complete overview of the physical oceanography of the area, mainly in its mesoscale aspects, of which there are few published studies, and the implications for early fish life history stages. The results showed the existence of two space and temporal scales for most of the physical processes that occur in the Bay of Biscay, a macroscale for seasonal time periods and a meso and submesoscale for the periods between seasons. The importance of local phenomena, such as upwelling or the variability of the Poleward Current, was observed. The interaction of both scales on these physical processes is discussed and the need for sampling at the submesoscale level to determine the distribution of ichthyoplankton is considered. Moreover, the mesoscale physical oceanography study is essential to improve the knowledge of interactions between strategies and environmental conditions that result in a significant mortality reduction in fish early stages.

This study focuses on the synchronous blooms of the coccolithophore Emiliania huxleyi and three dinoflagellates Prorocentrum micans, Ceratium furca var. furca and Ceratium fusus var. seta observed between 7 June and 11 July 2003 in the Dardanelles. An analysis of the vertical distribution of the E. huxleyi population size with respect to various environmental parameters was discussed. Additionally, inorganic nutrients and phytoplankton interactions were investigated in relation to the bloom conditions and hydrography of the Dardanelles. The algal bloom started in nearby Izmit Bay (eastern end of the Sea of Marmara) in early June, then quickly spread through the Sea of Marmara and continued until mid-July. Thermal stratification was observed between different water masses at the time of sampling. During the bloom period, cell density of E. huxleyi ranged from 3.58 × 107 to 2.55 × 108 cells l−1 in the superficial layer. Prorocentrum micans was the second most-abundant species and the cell numbers ranged from 1.0 × 106 cells l−1 to 3.3 × 106 cells l−1. Other abundant species in this area included C. furca var. furca and C. fusus var. seta.

The T-POD (Timing POrpoise Detector) is a self-contained acoustic data logger used for detecting and monitoring the presence of echolocation clicks of small cetaceans. It has become a standard tool in environmental impact assessments and monitoring programmes. Yet, little is known about the variability in sensitivity and detection range of T-PODs. In this study the field performance of ten v3 T-PODs was compared to detection thresholds measured in a tank. The T-POD thresholds ranged from 123 to 132 dB re 1μPa (pp). The detection thresholds of the ten individual T-PODs were different and the differences increased over time. The more sensitive a T-POD was in the laboratory (i.e. the lower the threshold) the more clicks were recorded by it in the field. Threshold correlated differently to the five analysed T-POD parameters (encounters, encounter duration, waiting time, porpoise positive minutes, clicks per porpoise positive minute). This study demonstrates that individual threshold calibrations of T-PODs are necessary to obtain comparable results when monitoring odontocetes with this tool. Regression equations for relationships between T-POD detection thresholds and study parameters obtained during field trials may allow comparisons of T-PODs with different detection thresholds.

Lake Vouliagmeni (Attica, Greece) is a lagoon of great scientific interest due to its endemic fauna, widely used for recreational activities. Understanding the dynamics of this peculiar ecosystem is essential for its conservation. An ecological survey of the benthic communities was carried out, in both spatial and temporal scales. Material was collected with SCUBA diving, by taking off samples from the principal habitats of the lagoon, i.e. meadows, soft and hard substrata. The identification of the collected 61,975 living specimens revealed the presence of 12 floral and 20 faunal species. Multivariate analyses separated the sampling sites according to the four different habitats of the lagoon, whereas no temporal patterns came up. Micrograzers were the dominant trophic group, followed by deposit feeders regardless of the habitat studied. Lake Vouliagmeni is among the less diverse Mediterranean lagoons, mostly due to its isolation from the sea that hinders the entrance of marine species.

Coralline algae are important reef-builders which can form nodules, known as rhodoliths, occurring worldwide in beds sustaining a high biodiversity. Although considered a non-renewable resource, they are exploited as a source of calcium carbonate used mainly for agricultural purposes. In Brazil between 96,000 and 120,000 metric tonnes of rhodoliths are extracted per year. Besides the direct impact caused by removal on the coralline bed, the dredge process may also produce a plume of fine sediment, which can change the primary production of the remaining organisms. In this study, four treatments, with three replicates, were used to acquire Lithothamnion sp. net photosynthetic rates with and without a sediment layer using a Clark-type oxygen microelectrode and micromanipulator. The results demonstrated that, under controlled conditions, the addition of a thin sediment layer resulted in a 30% reduction of the irradiance, decreasing the Lithothamnion sp. net production in 70%. For this reason direct and indirect effects of mechanical exploitation of the rhodolith beds should be included in future studies that focus on environmental impacts of dredging activity, whether it is linked to the extraction of these algae.

Habitat fragmentation from natural or human-mediated causes is a common phenomenon in terrestrial and aquatic environments. In this study, the effects of varying the size of habitat patches on the abundance of benthic invertebrates inhabiting date mussel (Musculista senhousia) patches was studied at two different transition environments, the Goro Lagoon (Adriatic Sea) and the Padrongiano Delta (Tyrrhenian Sea). Benthic fauna responded to habitat patchiness in a complex manner that varied according to habitat type, taxon and animal body size (small: 0.5–2.0 mm; large >2 mm). Small invertebrates were mostly polychaetes, nemertea, amphipods and isopods. Large invertebrates were mostly large polychaetes, bivalves, gastropods and crabs. Invertebrate population size and diversity seemed to be maximized in landscapes that include both small and large patches of mussel beds ‘embedded’ in a continuous matrix. Musculista senhousia patches served as a critical refuge and foraging habitat for many species. Patchy and continuous areas may promote the persistence of organisms with different life histories, especially in environments like those studied where mussel patches represent the only structural refuge available.

A new contribution on spatial and seasonal variability of physico-chemical parameters of the Golfo San Jorge benthic system from autumn 2001 through summer to 2002 is presented. Temperature, salinity, density, oxygen content and chlorophyll-a in bottom water as well as concentration of total organic matter, total organic carbon, total nitrogen, total phosphorus, chlorophyll-a and phaeopigments in sediments were analysed. The origin and nutritional value of the deposited organic matter were also assessed. The results reflect the existence of: (1) a typical temperate water seasonal cycle; (2) a bimodal cycle in the phytoplanktonic production; and (3) seasonal variations in the chemical variables and in organic matter origin in sediments.

Three sectors which geographically correspond with those identified in previous studies were defined: (1) the inner area of the gulf; (2) the areas next to the north and south extremes; and (3) the coastal and south-east part.

Coastal areas, in general, are affected more and more by anthropogenic activities. Benthic macrofauna assemblages react to this disturbance and constitute, then, an effective biological tool to study the degree of contamination of the biotope. For this study three coastal sites, more or less exposed to anthropogenic activities but differing according to their opening to the sea, were studied. Sediments were sampled aboard a research vessel and using a 0.1 m2 Van Veen grab. Results show that Tunis bay and Dkhila coast, which are more open to the sea, appear more balanced on the trophic plan, and the biodiversity state is more satisfactory. However, Bizerte lagoon is closed, except for a limited communication with the sea via a narrow ship canal. So, the ecosystem presents some eutrophication signs and a great trophic imbalance in which carnivores largely dominate the benthic assemblages. In this situation, the herbivore chain is substituted by a microbial chain and only some opportunistic species can survive in these anoxic sediments related to the strong fluctuations of the environment factors during the year.

Decapoda taken in Continuous Plankton Recorder (CPR) samples from the Pacific in 1997 and 2000–2003 have been identified and measured. Some previously un-described larval stages were referred to species and characteristics of these are described. Distributions and seasonal occurrence of decapod taxa in the samples are described and discussed with particular emphasis on the dendrobranchiate shrimp Sergestes similis and the brachyurans Cancer spp. and Chionoecetes spp. There is a prolonged larval season at low levels of abundance off the Californian coast but in the more northern waters there is a shorter productive period but numbers of larvae per sample are high, particularly in June. Larvae of Chionoecetes and other Oregoninae were found only from May to July.

The present study investigates the species distribution patterns and macrofaunal assemblages along the English Channel and the environmental factors contributing to observed patterns. Seven distinct macrofaunal assemblages were identified based on Hamon grab samples. In the western Channel, an Echinocyamus/Nemertea assemblage dominated, giving way to an Abra/Scalibregma assemblage in inshore waters. A Verruca/Sabellaria assemblage was identified to occupy large regions of the mid-Channel while those of the east Channel were more spatially variable. While variations in depth, sediment particle size and wave and tidal stress were significantly related to variations in assemblage structure, temperature did not appear to be greatly influential. In addition, acoustic data obtained for each station sampled allowed us to determine how representative the observed biological communities are over spatial scales somewhat larger than the sampling points. In contrast to earlier comparable studies using anchor dredges, the biological communities sampled in this study did not exhibit a large east–west distinction; the most abundant species and key assemblages were found to be present along the length of the Channel. The possible reasons for these differences with earlier studies are discussed.

The aim of this study was to analyse the tolerance of the planktonic stages of Psammechinus miliaris to hydrostatic pressure and temperature. Embryos of Psammechinus miliaris were subjected to different combinations of pressure and temperature for 3, 6 and 12 h. The percentage of embryos at each stage and the percentage of embryos developing abnormally were measured. Larvae at the gastrula and prism stages were subjected to pressure and temperature combinations for 24 h and the larval survival was calculated measuring the percentage of swimming larvae. Both embryos and larvae could survive at greater pressures than the known adult depth limits. Larvae showed a much greater potential than embryos for surviving deeper, with approximately 100% of both gastrulae and prisms surviving up to 200 atm at 5°C. These results are similar to other shallow-water species of Echinoida. Thus larval tolerance of high pressure and low temperature may have been important for the success of this group in colonizing the deep-sea.

A growing body of literature shows that benthic communities are hierarchically structured on spatial and temporal scales. In two study locations at Helgoland (North Sea), the northern and the western locations, we: (1) investigated the variation in abundance of specific algae and invertebrates at two spatial scales; and (2) evaluated the relationship between elevation and specific species at these scales. We were also interested in using this information about the spatial pattern of individual algae and invertebrates as well as the patterns of elevation to help develop a monitoring programme of the rocky intertidal. We examined the variation of individual algae and invertebrates by means of a hierarchical nested design. Data were taken from five replicates per plot, with plots located in transects (two transects per location).

At the northern location, the highest variability in cover of most algae and invertebrates occurred at the scale separated by about 50 m (scale: transect). This was a direct result of differences between the high- and the low-shore. Most species at high-shore showed a relatively low frequency of occurrence in contrast to a highest frequency of occurence (~100%) and maximal values of cover at low-shore. However, neither a linear nor a non-linear relationship between elevation and the specific species occurred. At the western location, the highest variability in most macroalgae and invertebrates investigated was among replicates (10s of centimetres apart). No relationship between elevation and individual species occurred at this location. Macroalgae at both locations were more consistent over time than invertebrate species. Our results suggest that the relevant processes shaping the individual macroalgae and invertebrates at the Helgoland rocky intertidal vary between locations and the specific species.

The potential causes of variation in macroalgal and invertebrate species at different spatial scales are discussed and suggestions for a future monitoring programme are given. Temporal inconsistency in the spatial patterns, and the fact that some individual algae and invertebrates comprising the benthic assemblages vary at different scales, speak in favour of a multiple-scale sampling approach for monitoring change in the intertidal communities at Helgoland.

Although the anthropogenic impact on Posidonia oceanica meadows in the Mediterranean Sea has been studied over the last few decades, the data about the status of this endemic magnoliophyte are scarcer from the Adriatic Sea. Samples of P. oceanica meadows were collected in June and July 2004 using SCUBA diving at 8 sites in the area of the Dugi Otok Island, all at depths of 10 m. The meadow's shoot density was measured, and shoots were collected to be examined and compared through number of leaves per shoot, leaf surface per shoot, leaf area index, number and biomass of taxa of epiphytic flora. Significant differences in P. oceanica meadow structure were found among investigated sites, especially between sites in the vicinity of the fish farm and the other sites. Meadow density decreased at sites in the Dugi Otok channel and the main impact factors seem to be the input of organic matter, originating from the fish cages and sewage input. These human activities are a source of nutrient pollution and stimulate blooms of phytoplankton and higher algae. The sea grass meadow vitality seems to be more negatively affected in the channel. The highest values of shoot density were recorded at investigated sites VR and ME at the outer part of the Dugi Otok Island. The shoot density was very low at site FU, situated in the channel. Biomass of the epiphytic algae exhibited the highest values at the site FU, while at the other investigated sites the values were significantly lower. Concerning the epiphytic macroflora, a total of 55 taxa of epiphytic macroalgae were identified and the class Rhodophyta dominated in all samples. The present study shows the high differences in morphological and structural characteristics of Posidonia oceanica meadows among various sites with and without anthropogenic influence.