Long-Term Changes in Shallow-Water Fouling Communities of the White Sea

The replacement of an ascidian (Styela rustica L.) fouling community by a blue mussel (Mytilus edulis L.) community was described for the White Sea. The alternation of populations of these two species takes place in fouling communities developing in the upper 3- to 5-m layer of water. The life span of each type of fouling probably depends on interannual climate fluctuations.     

Heart rate variation patterns in some representatives of Bivalvia

The pattern of heart rate variation was studied in bivalves sublittoral (aquaculture) and littoral mussels Mytilus edulis L. and Hiatella arctica L. in a long-term experiment at constant salinity (25‰) and temperature (10°C). Periodic changes in heart rate were observed in both littoral and sublittoral mussels. Heart activity could regularly decrease up to temporary cardiac arrest. Changes in H. arctica heart rate were much less pronounced compared to mussels and no cardiac arrest was observed.     

Effect of excretory-secretory products of some fouling organisms on settling and metamorphosis of the larvae of <Emphasis Type="Italic">Styela rustica</Emphasis> (Ascidiae)

The effect of the excretory-secretory products of some fouling animals on the settling and metamorphosis of larvae of the solitary ascidian Styela rustica was assessed. The substances secreted by the sponge Halichondria panicea stimulated settling of larvae, but concurrently blocked their metamorphosis. The excretory-secretory products of the mussel Mytilus edulis and the ascidian Molgula citrine did not affect settling of the S. rustica larvae but impeded their subsequent development. Water conditioned by the bivalve Hiatella arctica, stimulated settling and, apparently, metamorphosis of the larvae of S. rustica. The chemical substances produced by adult individuals of S. rustica facilitated settling of conspecific larvae but slightly delayed their metamorphosis.     

Experimental study of the ability of the sponge <Emphasis Type="Italic">Halichondria panicea</Emphasis> (Porifera: Demospongiae) to compete for a substrate in shallow-water fouling communities of the White Sea

The ability of the sponge Halichondria panicea to assimilate into the fouling communities of the blue mussel Mytilus edulis and the solitary ascidian Styela rustica has been studied in a field experiment, in which sponge fragments have been introduced artificially into epibenthic communities. The growth of H. panicea was suppressed greatly in the presence of young mussels; its survival rate averaged 40%. In the communities where S. rustica dominated, the survival rate of H. panicea reached 100%, but the growth rate was lower than in the control group (without competitor species). Despite the high natural growth rate and toxicity, the settlement success of H. panicea was low on the substrate occupied by another fouling species.     

A comparative study of the pumping activity of some fouling animals from the White Sea

The pumping activity of the bivalve Mytulus edulus, Hiatella arctica, and solitary ascidian Styela rustica from the White Sea has been studied. The dependence of the pumping activity on the mass and size of animals has been analyzed. It was shown that the mussel is the most active filter-feeder, that the least value of the pumping activity has been registered for H. arctica, and that S. rustica occupies an intermediate position according this index. The results obtained are examined in connection with the competitive relationship of the animals in the fouling community.     

The impact of waterborne cues from conspecifics and other species on the larvae of Halichondria panacea Pallas, 1766 (Porifera: Demospongiae)

The impacts of different concentrations of the excretory-secretory products (ESPs) of the solitary ascidian Styela rustica (Linnaeus, 1767) and the sponge Halichondria panacea (Pallas, 1766) on the settlement, metamorphosis, and mortality rates of H. panacea larvae were studied in a laboratory experiment. At high concentrations, substances released into the environment by the ascidian S. rustica exerted a negative impact on the metamorphosis rate of sponge larvae. The exposure to moderate or high concentrations of ESPs from conspecific adults led to high mortality of larval sponges; however, low conspecific ESP concentrations markedly stimulated metamorphosis; larval mortality was low. Apparently, different concentrations of the same ESPs can have effects with a different strength and focus. This should be taken into account in the study of chemically mediated interactions between aquatic organisms.     

Fouling Communities of Mussel Aquaculture Installations in the White Sea

We have classified fouling communities developing on artificial substrates of mussel mariculture plants in Kandalakshskii Bay of the White Sea. Several major types of fouling have been distinguished: mussel fouling; fouling similar to the epifauna of the benthos biocenosis of Laminaria saccharinadominated by the ascidian Styela rusticaor sponges Halichondria paniceaand Halisarca dujardini; young fouling developed by algae and the ascidians of the genus Molgula; and ecotone communities in-between these types of fouling. The characteristics of the distinguished communities are provided.     

Effect of excretion-secretion products of some fouling species on the biochemical parameters of blue mussel <Emphasis Type="Italic">Mytilus edulis</Emphasis> L. (Mollusca: Bivalvia) in the White Sea

The effect of excretion-secretion products (ESP) of five abundant fouling invertebrate species (bivalve mollusks Hiatella arctica and Mytilus edulis, solitary ascidia Styela rustica, sponge Halichondria panacea, and sea star Asterias rubens, inhabiting the White Sea) on the biochemical status of blue mussel M. edulis was assessed by the dynamics of lysosomal enzymes activity (nucleases, glycoside hydrolases, and cathepsins). ESP of conspecific species had no effect on the metabolism of the mollusks of this species. ESP of A. rubens, S. rustica, and H. panicea activated the same enzymes. First, acid RNase and glycoside hydrolases activity increased, but in different ways. The metabolites of H. arctica affected the activity of proteometabolism enzymes.     

Modulating role of lipids and their fatty acids in adaptation of the White Sea mussels <Emphasis Type="Italic">Mytilus edulis</Emphasis> L. to environmental salinity change

Role of lipids and fatty acids (FA) in littoral and sublittoral White Sea mussels Mytilus edulis L. was studied at various stages of reproductive cycle in the phenotypic adaptation (acclimation) to changes of the sea water salinity. The obtained data indicate differences in the mussel lipid and fatty acid spectra, which are connected both with their location (littoral or sublittoral) and with the spawning period stage (3b—release of gametes or 3c—resorption of residual sex products). Lipids and FA of both mussel groups respond to the salinity changes to the greater degree at the 3b than at the 3c stage. In the littoral mussels at the 3b and 3c stages there were revealed differently directed changes in the content of membrane lipid—cholesterol—and in the cholesterol: phospholipids ratio. In the sublittoral mussels that are less adapted to extreme action of abiotic factors, more significant changes were found in the lipid and FA compositions.     

Mutual effects of several fouling organisms of the White Sea (<Emphasis Type="Italic">Mytilus edulis,Styela rustica</Emphasis>, and <Emphasis Type="Italic">Hiatella arctica</Emphasis>) on their growth rate and survival

The mutual effects of several fouling species (the bivalves Mytilus edulis and Hiatella arctica and a solitary ascidian Styela rustica) on their growth rate and mortality were studied through field experiments. The interactions between S. rustica and H. arctica appeared to be the least antagonistic. In contrast, the mussel was the most “aggressive” species with regard to both competitors. It was observed that the ascidians died, because they were intensively braided and gummed up with the byssus threads of the mussels. However, in some cases the intraspecific competition was stronger than the interspecific one.