The genus Dinophysis in the Southern Adriatic Sea

Abstract

Some preliminary results of a survey carried out along the Southern Adriatic coasts (Brindisi-S.M. Leuca) are reported in order to contribute to the knowledge of the phytoplankon community of this area. Ten Dinophysis species had been identified, four of them are known to be involved in DSP mussel contamination. Spatio-temporal distribution of Dinophysis spp. is shown.     

Phytoplankton and chemico-physical parameters of the Scardovari Lagoon (Po Delta,North Adriatic Sea) during 1991 and 1992

Abstract

During research directed towards the employment of the biological resources of the North Adriatic lagoons, from January 1991 to December 1992, in both tidal phases, a survey was carried out on the phytoplankton and the chemico-physical parameters of the Scardovari lagoon. Data analyses allowed two different areas to be distinguished: one inner, which was generally characterized by high phytoplanktonic densities (St. 3–4), the other outer, which was more influced by marine load (St. 1–2). Photosynthetic picoplankton was dominant in terms of cell number in most samples. Phytoplanktonic fraction >2 μm was represented mainly by diatoms, which showed the higher species number. During the sample observation, some dinoflagellates, considered toxic or potentially toxic, were found. Their presence was important because of their effect on the bivalve mollusc cultures.     

The role of modelling in the control of toxic blue-green algae

Blooms and scums of blue-green algae (cyanobacteria)have occurred throughout the world for many years andare only one of many problems associated withover-enrichment by nutrients of fresh and marinewaters. Although much studied and written about,eutrophication poses complex and difficult managementproblems. The role of modelling as an aid to thecontrol of blue green algae is discussed.     

The occurrence of Gonyaulax tamarensis Lebour bloom in the Adriatic Sea along the coast of Emilia-Romagna

Abstract

The authors describe the occurrence of Gonyaulax tamarensis Lebour bloom in the Adriatic Sea between 200 and 1000 m off the coast of Emilia-Romagna during the period of August 14-20 1982.     

The evolution and phytoplankton composition of mucilaginous aggregates in the northern Adriatic Sea

Recurrent occurrences of visible mucilage “clouds” that cover areas up to several hundred kilometres with vertical dimensions of 20–30 m have been recorded in the stratified water column in the northern Adriatic. In the past this was described as “mare sporco” phenomenon. Past studies of the phenomenon indicated that phytoplankton is an important component of mucilage. Our research revealed the composition of phytoplankton assemblages in different types of mucilaginous aggregates collected during the summers of 1997 and 2000 using pigment biomarkers (HPLC). Phytoplankton biomass in the mucilage samples was very high, ranging from 7.9 μg g⁻¹ to 390.8 μg g⁻¹ of chlorophyll a per unit of dry mass of mucilage. The phytoplankton community in the early, loose stage of mucilaginous aggregates was heterogeneous, as indicated by the diversity of detected pigments. The number of phytoplankton groups decreased as the aggregates aged and diatoms increased in relative biomass (up to 92.7%). Phytoplankton biomass in seawater was similar in years with and without mucilage; however, significantly higher contributions to the total biomass of 19′-hexanoyloxyfucoxanthin-containing phytoplankton (prymnesiophytes) were found in the upper 10 m in spring of the “mucilaginous years” (1997 and 2000) followed by prevalence of diatoms in summer. The F_p pigment index used to assess seawater trophic conditions reached lower values in April–May in mucilaginous years (1997 and 2000) compared to non-mucilaginous years (1998 and 1999). We conclude that the role of prymnesiophytes and other small flagellates is crucial for the initial phases of mucilage appearance. Aggregates represent a favourable environment for the secondary development of opportunistic diatoms that foster mucilage formation.     

Diatom distribution in the Southern Adriatic Coastal waters

Abstract

Data on the horizontal and vertical distribution of diatom species, collected between April 1995 and March 1996 in coastal waters of the Apulian Adriatic Sea are presented. A total number of 120 species belonging to 51 genera were identified. Diatoms were dominant in the major part of the examined samples, constituting up to 90% of the total cell numbers during the spring period.     

Phytoplankton population density and volume as indicators of eutrophication in the eastern part of the Adriatic Sea

Population density and volume-biomass of microplankton, nanoplankton and total phytoplankton were analyzed at 14 stations along the eastern part of the Adriatic Sea. Based upon data frequency distribution, four categories of ecosystems were established in the investigated area. Criteria for ecosystem categorization and biological evaluation of eutrophication are proposed.     

Temporal variability of particulate organic carbon,nitrogen and phosphorus in the Northern Adriatic Sea

The particulate organic carbon (POC), nitrogen (PN) and phosphorus (PP) vertical distribution along the water column and temporal variability in coastal and offshore waters of the Northern Adriatic Sea were related to the hydrodynamic conditions and biological processes. Fresh water inputs from the Po and Adige rivers enhance primary production, resulting in high POC, PN and PP concentrations at the surface. In offshore waters, POC and PN concentrations were about 3–4 times less than in the coastal waters, while PP were up to 10 times lower, highlighting a marked phosphorus depletion. In the bottom layer, the POC content decreases due to the strong density gradients which separate bottom waters with prevailing degradation processes. Short term 48 h-variability of POC, PN and PP in the coastal waters was determined to a great extent by variations in the spreading of river plumes at the surface and by nepheloid layers and resuspension processes in the bottom waters. The particulate matter in the Adriatic offshore waters is extremely depleted as regards particulate phosphorus and is characterised by C_org:P and N:P ratios higher than the Redfield ratio.     

Hyperbenthic gobies in the Kvarner area, Adriatic Sea

By the aid of SCUBA diving in the Kvarner area (northern Adriatic) from 1993 to 2002 five gobiid species were found to be hyperbenthic. These findings provided specific data on their ecology.     

Chattonella marina (Raphidophyceae), a potentially toxic alga in the Salton Sea, California

Chattonella marina was found in high abundance in the phytoplankton of the Salton Sea from April to November, 1997. Maximum mean density was over 600 cells ml^–1 mid-lake. It was not detected from January 1997 to March 1997 or in January and February 1998. Transmission electron microscope studies show the typical Chattonella features: a teardrop-shaped nucleus, numerous radially arranged chloroplasts and lack of a cell wall. Gills of fish collected at the height of the Chattonella bloom showed damage to the primary and secondary lamellae and increased numbers of mucus cells. To our knowledge this is the first report of a species of Chattonella in a salt lake.     

The extensive development of the turf-forming red alga Womersleyella setacea (Hollenberg) R. E. Norris (Rhodophyta,Ceramiales) in the Bay of Boka Kotorska,Montenegro (southern Adriatic Sea)

Abstract

In August 2003, dense turfs formed by the filamentous red alga Womersleyella setacea (Hollenberg) R. E. Norris were found in the open part of the Bay of Boka Kotorska, on the shore of Montenegro (southern Adriatic Sea). The habitat and morphology of the alga are described and the impact of the massive development of this species on the structure of the algal communities is discussed.     

Vanneaugobius dollfusi Brownell, 1978 a rare fish new to the Adriatic Sea

Two specimens of Vanneaugobius dollfusi found among ichthyological material of the Institute of Oceanography and Fisheries, Split and two specimens donated to the Natural History Museum Rijeka provide the first positive records of this species in the Adriatic Sea, and the second record ever for this species.     

Seasonality of Dinophysis spp. and Prorocentrum lima in Black Sea phytoplankton and associated shellfish toxicity

Plankton surveys, between 2001 and 2005 along the Russian Caucasian Black Sea Coast, revealed Dinophysis rotundata, D. caudata and Prorocentrum lima as the most ubiquitous of the known dinoflagellates associated with diarrhetic shellfish poisoning (DSP). Dinophysis spp. were first observed during the spring phytoplankton succession and persist throughout the late summer phytoplankton peak. The highest total concentration, 3000 cells/L, of D. rotundata and D. caudata was observed in April 2001. Unlike Dinophysis, P. lima was rarely observed in plankton samples but closely followed storm events with maximum cell counts of P. lima occurred in July 2002.The presence of Dinophysis in mussel (Mytilus galloprovincialis) hepatopancreas correlated with concentration with Dinophysis observed in the plankton samples. Conversely, P. lima could be found in most hepatopancreas samples collected during the May to October period. Therefore, planktonic concentration of P. lima does not reflect its availability for and consumption by shellfish.Samples of mussel hepatopancreas, from August 2002, with a corresponding Dinophysis concentration of 250 cells/L and no observable P. lima, were found to contain 0.03 ng OAE/g. This sample analyses by LC-MS/MS displayed okadaic acid (OA) and related congeners (DTX1) along with the pectinotoxins (PTX2 and PTX2sa). Highest observed levels of P. lima-induced DSP-toxicity in hepatopancreas was 0.41 g OA-equivalents/g corresponded to the highest observed planktonic cell counts of P. lima, 300 cell/L in August 2001. Cultures isolated from this sample were found to produce OA, DTX1 and their related diol esters.These data reveal a threat, represented by DSP-toxic species, at Black Sea coasts, and provide grounds for the introduction of phycotoxin control measures in the region.     

Occurrence ofDinophysis spp. and toxic shellfish in the Northern Adriatic

The dynamics of the toxicity of the musselMytilus galloprovincialis was compared between two different shellfish farms, 5 km apart, but using the same cultivation technique. The main differences concerned the freshwater influx and the open aspect to the Gulf of Trieste. It is suggested that a deep closed bay and abundant fresh water inflow are the two main conditions for the low toxicity levels in mussels and for shorter periods of danger. A detailed study of the phytoplankton samples revealed the presence of eight species ofDinophysis in the area of both shellfish farms. During the period of the DSP outbreak in Slovenia (autumn and winter 1989).D. fortii andD. acuminata were the most frequentDinophysis species. There was a high positive correlation between the onset of mussel toxicity and the appearance ofDinophysis spp.     

First record of the Norway goby in the Adriatic Sea

One male and four female Norway gobies Pomatoschistus norvegicus are reported from the Adriatic Sea.     

The effects of northern italian rivers and Eastern Mediterranean ingressions on the phytoplankton of the Adriatic Sea

An analysis of the distribution of the phytoplankton standing crop during a period of high stability characterized the relative influence of northern Italian rivers and Mediterranean waters on the Adriatic Sea. The region influenced by northern Italian rivers was marked by low community diversities, relatively high chlorophyll a standing crops and cell densities, high microplankton to nannoplankton community volume ratios, and the dominance of Nitzschia seriata. To the contrary, the region influenced by Mediterranean waters exhibited high community diversities with prominent oceanic and warm water elements, low chlorophyll a standing crops and microplankton cell densities, low microplankton to nannoplankton ratios, and a relatively conspicuous coccolithophore flora.Nannoplankton populations remained relatively constant throughout the Adriatic. However eutrophication resulted in a marked increase in the microplankton component of the community, with the diatom Nitzschia seriata serving as a prime indicator of the process, even in regions several hundred kilometers downstream from nutrient sources.Even under relatively low rates of river discharge, the influence of northern Italian rivers could be traced along the entire western sode of the sea to the Otranto Strait, with low north to south and high west to east gradients resulting from the effect of a cyclonic surface circulation pattern on inflowing Mediterranean waters in the south and river discharge in the north.     

Neonatal and juvenile sandbar sharks in the northern Adriatic Sea

The occurrence of neonatal sandbar sharks Carcharhinus plumbeus in the Adriatic Sea is reported; however, nursery areas still need to be identified.     

Ecology and taxonomy of potentially toxic Pseudo-nitzschia species in Lim Bay (north-eastern Adriatic Sea)

The population dynamics of Pseudo-nitzschia in relation to environmental factors was investigated from March 2002 to July 2008 in Lim Bay, in the north-eastern Adriatic Sea. Domoic acid was monitored in the breeding population of Mytilus galloprovincialis from 2005 to 2008. The principal-component analysis of environmental parameters showed that the system is mostly temperature driven. The phytoplankton community was mainly composed of diatoms. Pseudo-nitzschia was the dominant diatom, present in 60% of samples, with a maximum (1.6 × 10⁶ cells L⁻¹) contribution up to 97% of the total diatom abundance. Morphological analysis revealed Pseudo-nitzschia manii and potentially toxic Pseudo-nitzschia pseudodelicatissima, Pseudo-nitzschia pungens, Pseudo-nitzschia fraudulenta and Pseudo-nitzschia calliantha as the dominant species in blooms. Pseudo-nitzschia abundance positively correlated to temperature, phosphate and ammonia in accordance with its maximal abundance in the summer/autumn period when fish farms had a maximum impact on the environment. Domoic acid was detected in M. galloprovincialis in concentrations below regulatory limits, ranging from 0.097 to 0.8721 μg g⁻¹ in five cases from April to October 2005 in Lim Bay, but so far it is not clear which of the species was responsible for DA production. This study is also the first record of P. manii, P pungens and P. fraudulenta species in the Adriatic Sea.