Volume 51, Issue 6

Annual dynamics and ecological characteristics of the genus Dinophysis spp. and associated shellfish toxicity events were studied from 2001 to 2005 during monitoring fieldwork in the coastal waters of the eastern Adriatic Sea. Analysis of the seasonal occurrence of Dinophysis species identified D. acuminata and D. sacculus as typical spring species, D. caudata , D. fortii and D. rotundata as summer and late summer species and D. tripos as a winter species. The highest abundances occurred when there were large differences between surface and bottom temperatures and salinities. D. caudata , D. sacculus and D. rotundata abundances had significant relationships with Δt, while the highest abundances of D. acuta , D. fortii and D. tripos were associated with high Δs values. Much higher abundances of D. caudata and D. fortii in offshore compared to inshore waters of the northern Adriatic Sea and the significant inverse relationship of these species' abundances with salinity suggested the possibility of their transport by Italian river-influenced coastal waters towards the eastern Croatian coast during the summer season and under stratified conditions. Toxicity events occurred more frequently in the more eutrophicated northern Adriatic Sea than in the southern Adriatic Sea and mostly succeeded the rainfall periods. Diarrhetic shellfish poisoning (DSP) toxin profile analyses identified okadaic acid and yessotoxin as the main DSP toxins occurring in Croatian waters.

One of the peculiarities of subtidal rocky assemblages of the Mediterranean Sea in comparison to other geographical regions is the development of important biogenic structures in deeper habitat that can influence coastal diversity. We compared species composition, alpha diversity, functional diversity and patterns of spatial variability between shallow and deep subtidal macroalgal assemblages of the Mediterranean Sea. Shallow and deep assemblages differed greatly both in species composition and abundance of morphological groups, leading to high between-habitat (beta) diversity related to a depth gradient. Moreover, patterns of spatial variability changed between habitats, resulting in greater large-scale variability in shallow habitat and greater small-scale variability in deep habitat. Finally, deep assemblages had a greater number of species than shallow assemblages. These findings have important implications for the management of Mediterranean coastal systems.

The capacity of Ulva rigida as a bioindicator of Zn, Cu, Pb and Cd contamination in oligohaline coastal waters was investigated. Metal concentrations in U. rigida , water and sediments and several environmental variables were measured seasonally at four stations in the coastal section of the Evros River Delta, Aegean Sea. All four metals in sediments had a significant local variation; in particular, they decreased with increasing distance from the fluvial end-member of Evros River. Mean Zn, Cu, Pb and Cd concentrations in U. rigida were 61.0, 22.4, 6.1 and 1.1 μg g -1 dry weight, respectively. This macroalga, compared to other co-occurring macroalgal species, had a high metal accumulation capacity, mainly of Cu and Cd. Local patterns of Zn, Cu and Pb in U. rigida were similar to those in sediments, while that of Cd was not; moreover, Cu and Pb in U. rigida correlated positively with their sediment contents, suggesting that this seaweed satisfies the basic prerequisite for a bioindicator of these elements in oligohaline environments. No metal in U. rigida displayed a significant seasonal variation, and there was no significant variation in ambient concentrations. A negative correlation between Zn in U. rigida and water salinity was found, probably due to both a higher metal burden in the freshwater flowing in the study area and to a decrease in Zn uptake with increasing salinity; Cd in the macroalga correlated negatively with water column ammonium.

The red alga Solieria chordalis was used as a model to investigate the effects of salt and light stress on the release of volatile halogenated organic compounds (VHOCs). We used a purge and trap technique coupled with a gas chromatograph equipped with an electron capture detector. S. chordalis was exposed to hyposaline (22 psu), hypersaline (50 psu) and normal salinity (34 psu) media in combination with light stress (48 h in the dark followed by 24 h under continuous light). The releases of 9 VHOCs (i.e., CH 3 I, CH 3 CH 2 I, CH 2 ClI, CH 2 Br 2 , CHBrCl 2 , CHBr 2 Cl, CH 2 BrI, CHBr 3 , CH 2 I 2 ) were measured after 0, 24, 48 and 72 h on algal sub-samples. In algae unstressed by salt, VHOC production rate decreased under dark conditions but increased with light exposure. However, long periods of light also resulted in higher production of di-halogenated compounds (as compared to tri-halogenated or mono-halogenated compounds). The results from salt-stressed samples indicate that hypoosmotic conditions strongly enhanced whole VHOC production rate, whereas hyper-osmotic conditions slightly reduced their production. An exception was mono-halogen production, which was higher under hyper-osmotic condition (especially during dark periods). Furthermore, long exposure to light and hyper-osmotic conditions led to a decrease in the production of di-halogenated compounds (this did not occur in thalli unstressed by salt). As halogen productions derive from different metabolic pathways, including an enzymatic mechanism, it is possible that the activity of these enzymes may be affected by exposure to various salinity conditions.

We studied the conservation status of a maërl bed off Benencia Island (NW Spain) over a 2-year period using SCUBA and dredging. The maërl bed, which includes a maërl beach, extended from the intertidal to subtidal zones (18 m), and occupied an area of 215 ha. It was composed of a pure unattached coralline algal deposit occasionally mixed with broken shells. The area estimated for the highest maërl cover (76–100%) was greater than reported in previous research. The living maërl layer reached 15 cm in depth and the living/dead maërl ratio was high (80–100% living maërl cover). The dominant maërl-forming species was Phymatolithon calcareum , although unattached plants of Mesophyllum sp. reaching 10 cm in diameter were found in two sites. Both maërl species are fruticose. The proportion of discoidal specimens of P. calcareum was related to depth. The associated flora comprised 137 species whose seasonal variations were very marked, with high floristic richness in summer (71 species) and low in winter (35 species). Crustose and turf-like species were the dominant floral components throughout the year, whereas the presence of other species was restricted to specific periods. We propose that Benencia Island be included in future Atlantic Iberian maërl bed conservation schemes.

We present an ultrastructure-based revision (using light and electron microscopy) of the type species of the genus Cocconeis , C. scutellum var. scutellum , and four often-mentioned but poorly described, morphologically related varieties: C. scutellum var. baldjikiana , C. scutellum var. c linoraphis , C. scutellum var. parva , C. scutellum var. posidoniae . In addition, we introduce three new taxa, C. scutellum var. gorensis var. nov., C. scutellum var. posidoniae f. decussata f. nov. and C. scutellum var. sullivanensis var. nov. The taxonomic relationships between these varieties and the remaining validly described C. scutellum varieties are analyzed on the basis of their ultrastructural differences. We also provide additional information on the geographical distribution of all analyzed C. scutellum taxa.

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