[Μπλε]

Αρχικό μήνυμα απο Physalia

προτείνω αρχικά google search για massive necrosis και mucilage events ή mucilaginous aggregates.

Αντιγράφω από:

Devescovi M and Ivesa L (2007) Short term impact of planktonic mucilage aggregates on macrobenthos along the Istrian rocky coast (Northern Adriatic, Croatia). Marine Pollution Bulletin 54(7): 887-893

Sedimentation of organic matter due to eutrophication is an important component of global changes affecting the coastal marine environment (Gray et al., 2002). Increased concentrations of nitrate and phosphate lead to the production of dissolved and particulate organic matter above natural levels in the water column and on the sea bottom ([Cadée, 1984] and [Smith, 1984]). The process of degradation of organic matter uses up oxygen; thus, in circumstances of decreased advective and vertical mixing, hypoxia and even anoxia may occur. In parallel with the oxygen decrease, concentrations of toxic ammonia and hydrogen sulphide are augmented, impacting marine organisms further (revised by Gray et al., 2002). In the northern Adriatic, specific features of the particulate organic matter are dense mucilaginous aggregates which can attain up to several meters in diameter ([Degobbis et al., 1995] and [Degobbis et al., 2000]).The first record of mucilage aggregates in the Northern Adriatic date back to 1729, and mucilage occurred episodically in the 19th and 20th centuries. However, from 1988 until now, mucilage aggregates have formed at varying degrees of intensity nearly every summer, severely affecting the fishery and tourism (Pompei et al., 2003). Thus, a considerable number of recent studies have been devoted to the mucilage phenomenon. It was stated that the mucilaginous material was due to extracellular polysaccharidic secretions produced by members of the phytoplankton during prolonged periods of calm and sunny weather, and with waters having a strong picnocline ([Vollenweider et al., 1995], Degobbis et al., 1999 D. Degobbis, A. Malej and S. Fonda-Umani, The mucilage phenomenon in the northern Adriatic Sea. A critical review of the present scientific hypotheses, Annali dell’Istituto Superiore di Sanità 35 (1999), pp. 373–381. View Record in Scopus | Cited By in Scopus (53)[Degobbis et al., 1999] and [Giani et al., 2005]).
In spite of the importance and widespread occurrence of the phenomenon, information about the impact of mucilage on benthic organisms of the infralittoral zone is scarce. Mucilage covering seagrass assemblages and causing the death of irregular sea urchins (Spatangus spp.) and fish of the genus Gobius was observed in the Piran region (Slovenia; Stachowitsch et al., 1990). On the rocky substratum (Isle of Rab, Croatia), mucilage retained by the complex ramified structures of gorgonians and macroalgae of the genus Cystoseira was observed (Stachowitsch et al., 1990). The intense smothering of benthic assemblages by mucilage may reduce the availability of light, nutrients, and oxygen, as well as accumulating ammonia and hydrogen sulphide. However, Müller et al. (1998) assumed that benthic organisms are killed even if they are only lightly covered by the mucilage because aggregates contain toxins which affect vital mechanisms of cell metabolism. Thus, mass mortality may occur on the shallow rocky bottom of the northern Adriatic during periods of mucilage formation (Müller et al., 1998).
Until now, the intensity and patterns of the impact were not assessed in the nearly horizontal shallow rocky substratum. This study is aimed to provide quantitative observations of the mucilage impact on organisms inhabiting this habitat. The obtained results could form the basis for future studies of the process of mucilage sedimentation which, similarly to other types of sedimenting material, could affect the function, composition, structure, and dynamics of the rocky coast assemblages (reviewed by Airoldi, 2003).
Due to their high abundance along the western Istrian coast, organisms selected for this investigation were the sponge Verongia aerophoba O. Schmidt, 1862 and the mollusc Arca noae Linnaeus, 1758 (Pérès and Gamulin-Brida, 1973). Cystoseira species were included because these perennial canopy-forming algae are involved in processes such as nutrient cycling and are considered essential habitat formers, providing shade and shelter for a diverse assemblage of animal and algae, thus enhancing biodiversity (Benedetti-Cecchi et al., 2001).