Zoobenthos-inhabiting Sarcotragus muscarum (Porifera: Demospongiae) from the Aegean Sea

The cavities and outer surfaces of 20 individuals of the sponge Sarcotragus muscarum collected from the Turkish Aegean coast during July–September 1993 contained a total of 148 zoobenthic species with 5299 individuals belonging to seven taxonomic groups. Among these, Polychaeta accounted for 60% of the total number of species, while Crustacea comprised 71% of the total number of individuals and 40% of the wet weight of biomass. The amphipod and decapod crustaceans Tritaeta gibbosa and Synalpheus gambarelloides, and the bivalve Hiatella arctica, were the most abundant species on the sponge samples both in terms of number of individuals and biomass values. The community structure inside the sponges was greatly influenced by the nature of the substratum around the sponge, and by the overwhelming population of the Lessepsian echinoderm Ophiactis savignyi. Number of species, biomass and diversity index values were found to be positively related to the sponge volume. Mean density and biomass of the associated taxa are 0.22 ind cm^–3 and 11.63 mg cm^–3, respectively.     

Macroinvertebrate drift in a Rocky Mountain stream

An extensive series of drift collections from a Rocky Mountain stream was used to investigate quantitative patterns in the taxonomic composition of drift throughout spring, summer and fall for 1975–1978. Drift was estimated by drift rate, the number of organisms drifting past a point per 24 h; and by drift density, the numbers of organisms collected per 100 m³ of water sampled.Drift densities were up to ten times greater by night than by day, and 24 h drift densities for the total fauna approached 2000 per 100 m³ in June–July, declining to <500 by autumn. Ephemeroptera, and especially Baetis, dominated the drift. Drift rates were greatest in late spring, around 10⁶ per 24 h, which are among the highest values reported for small trout streams. Drift rates declined to <10⁵ during the summer, and shifts in the taxonomic composition are described.Multiple regression analysis of the relationship between drift rate and density, and the independent variables discharge, benthic density and temperature, showed that discharge typically was a significant predictor of 24 h drift rate, usually the best single predictor. In contrast, 24 h drift density most frequently was independent of discharge, indicating that this measure tends to correct for seasonal variation in discharge, as suggested in the literature. However, this was not invariably true. Drift density significantly correlated with benthic density in five of eight taxa inspected, thus seasonal declines in the benthos probably accounted for parallel declines in drift density.     

New Phase of Succession of the Bivalve Abra ovata Community in Sulaksii Bay, the Caspian Sea

The study of the Abra ovata community existing on the flooded area of Sulakskii Bay in the Caspian Sea since the mid-1980s was continued. It was found that the pioneer species A. ovata and Cerastoderma glaucum still dominate in the community structure and define the course of succession despite a reduction in their population density and frequency of occurrence. The species composition and structure of the modern A. ovata community and the processes occurring in it are similar to the climax stage of the A. ovata community in the Middle Caspian Sea. Both mollusk species exhibit seasonal variations in number, which are due to predation by sturgeon and natural mortality. A steady annual decrease in the sea level, retreat of the water's edge by 80–100 m, and mass burial of the shells of bivalve mollusks in the drying-out innermost part of the bay were observed.     

Temporal and spatial distribution of chironomid larvae and oligochaetes in two Dutch storage reservoirs

Long-term changes in distribution and taxonomic composition of chironomid larvae and oligochaetes in two water storage reservoirs in The Netherlands were studied. A succession among the chironomid species was observed. In the last 10–15 years chironomid densities varied. Compared with other lakes chironomid densities were high. Densities of chironomids were higher in the littoral zone than in the profundal zone. The opposite was found for oligochaetes. Densities and composition of the chironomid fauna in the two reservoirs were similar.Procladius, Tanytarsus andHarnischia dominated at all depths. However, pupal exuviae samples showed some differences in chironomid taxonomic composition between the two reservoirs. Orthocladiinae, rarely found in bottom samples, abounded in pupal exuviae samples.     

Characterization of the bacterial flora of mass cultivated Brachionus plicatilis

Bacterial density and composition in association of mass cultivated rotifers (Brachionus plicatilis, SINTEF-strain) was investigated, during experimental conditions identical to the procedures used for preparing rotifers as live food for marine cold water fish larvae. These procedures include cultivation, enrichment with squid meal and acclimation to low temperature by storage of the rotifer culture at 6 °C. Large variations were observed in the number of rotifer associated (1.8–7.6 · 10³ colony forming units per rotifer^–1) and free-living (0.6–25 10⁷ cells·ml^–1) bacteria. An increase of 50–150% in the bacterial number was normally observed after feeding the rotifer with squid meal, but after three days of acclimation at 6 °C, the bacterial numbers decreased to the initial level.After enrichment of the cultures with squid meal, the similarity in the composition of the bacterial flora between the rotifers and water was reduced. However, acclimation of the culture at 6 °C resulted in better agreement of the rotifer associated flora and that in water. Enrichment of the cultures induced a shift in the bacterial composition from Cytophaga/Flavobacterium dominance to Pseudomonas/Alcaligenes dominance. The bacterial flora of the rotifer cultures are dominated by presumably opportunistic species after enrichment, which may have detrimental effects when rotifers are fed as live food to marine fish larvae.     

Effects of food quality on growth and biochemical composition of a calanoid copepod,Argyrodiaptomus furcatus,and its importance as a natural food source for larvae of two tropical fishes

Growth, reproduction and biochemical composition were analyzed for the copepod Argyrodiaptomus furcatus fed on the alga Ankistrodesmus gracilis grown in different media. The ingestion of this copepod by larvae of two species of tropical fishes was also evaluated. The mean peak density of the copepod population was 1369 individuals l^–1 for all four diets used, and the highest was 1387 individuals l^–1 on diet ARV (algae + ration + vitamins). A small copepod, A. furcatus tends to have a short life span. The smallest females did not attain maturity in the shortest time on all diets used. Food quality may play a major role in the dynamics of the biochemical composition of this copepod. Argyrodiaptomus furcatus was a more important food item for larvae of tambaqui (Colossoma macropomum) than of pacu (Piaractus mesopotamicus). However, it made up a large part of the gut contents of larvae of both species.     

Distribution Patterns and Size–Age Composition in Aggregations of the Gastropod Mollusk Nucella heyseana in Peter the Great Bay, Sea of Japan

Gastropods Nucella heyseana were collected from 1999 to 2001 from different habitats in Vostok Bay (Sea of Japan). The spatial distribution, the seasonal and interannual dynamics, and the composition of aggregations of this mollusk were analyzed. In Vostok Bay, N. heyseana inhabits biotopes that are typical of this species and other members of the genus and sometimes forms aggregations with an unusually high density and biomass (up to 1690 spec/m² and 3680 g/m²), thus exceeding 10–40 times the greatest values reported elsewhere for populations of the southern Kuril Islands and Pos'eta Bay (Sea of Japan). N. heyseana is a typical polyphagous predator, and its diet includes numerous species of the associated fauna of bivalve and gastropod mollusks (more than 30 species). The abundance, composition, and stability of local aggregations of N. heyseana are largely dependent on the abundance dynamics of its prey (primarily the most common species, such as Mytilus trossulus, Ruditapes philippinarum, Protothaca euglypta, and Littorina spp.). The opinion on the low density of N. heyseana in southern Primorye (Golikov, Kussakin, 1978) is probably based on a lack of information about the intertidal fauna of this region compared to the South Kuril Islands.     

Swimming Behaviour of <Emphasis Type="Italic">Chironomus acerbiphilus</Emphasis> Larvae in Lake Katanuma

We conducted a seasonal survey of the swimming behaviour of Chironomus acerbiphilus larvae in volcanic Lake Katanuma from April 1998 to December 2001. Swimming C. acerbiphilus density was much higher than other chironomid species in lakes. All C. acerbiphilus larvae (1st through 4th instars) swam, but the earlier instars (especially the 1st) had the greatest densities and fluctuations. First instars were never found in the benthic population. This result indicates that the 1st-instar larvae are planktonic. Low water temperature (below about 10 °C) resulted in the seasonal disappearance of swimming chironomid larvae. Chemical factors – oxygen depletion or presence of hydrogen sulfide – also restricted the distribution of swimming and benthic larvae. Larvae were distributed only in the oxygen-rich part of the lake bottom and swam only in the oxygen-rich layer of the water column. The density of older swimming C. acerbiphilus (3rd and 4th instars) tended to increase with increasing benthic larval densities. The chemical stress of oxygen depletion or presence of hydrogen sulfide during holomixis within and after the stratification period leads to conspicuous swimming behaviour of benthic C. acerbiphilus larvae. Almost all C. acerbiphilus larvae died on this occasion.     

Distribution and conservation significance of endemic species of flowering plants in Peru

Using the data published in the Catalogue of the Flowering Plants and Gymnosperms of Peru, we analyzed the elevational distributions of 5323 species reported as endemics from that country as a whole, for 10 families with the highest number of endemic taxa in Peru, and the distribution patterns of these species according to life form. We calculated the density of endemism (number of endemic species divided by area × 1000) and absolute number of endemic species among life forms and families, along an elevational gradient. Overall densities of endemics were 10–15 times higher at mid-elevation (2000–3500 m) than in the Amazonian lowlands (0–500 m). Absolute numbers of endemics peaked at 1500–3000 m for herbs, shrubs, and epiphytes, while trees, vines, and lianas showed maxima in the lowlands (0–500 m); yet densities of endemics for all life forms peaked at 1500–3000 m. Among the 10 families with the highest number of endemics, densities of endemics peaked at mid- to high elevation (1500–4500 m), but showed much disparity in the elevational distribution of absolute numbers of endemic species. Finally, the percentage of endemic species to total species is highest for herbs, shrubs, and epiphytes. Given that less than 10% of the land area for each of the montane zones (2000–4500 m) is protected compared to 13.5–29.9% in the lower elevations (0–1000 m), we recommend that priority be given to increasing the size of protected areas at mid- to high altitude in the Andean slopes to grant further protection in zones with the highest density of endemics. We also recommend that more emphasis be given to collecting and studying non-trees, since most endemic species belong to that class.     

Composition,Seasonal Dynamics,and Long-Term Fluctuations in the Density of Pelagic Polychaetes in Amurskii Bay,Sea of Japan

This is the first survey of the composition and seasonal density dynamics of the pelagic polychaete larvae in Amurskii Bay. This is a summary of the results of two years of observations (1996–1998). The larvae of 14 polychaete families have been recorded. The greatest number of species have been found in the family Spionidae. The most common were the larvae of Harmothoe imbricata (family Polynoidae) and Paraprionospio sp. (family Spionidae). The larvae of polychaetes have been found in plankton throughout the year and have two density peaks. The first peak was due to the spawning of H. imbricata; the second one was provided by representatives of several species of the family Spionidae, mostly Paraprionospio sp., Polydora ciliata, and P. caeca.     

Vertical Distribution of Zooplankton in a Strongly Stratified Hypertrophic Lake

The vertical and temporal distribution of metazooplankton in the small hypertrophic, strongly stratified, temperate Lake Verevi (Estonia) was studied during 1998–2001. The zooplankton of Lake Verevi is characteristic of hypertrophic lakes, with a small number of dominant species, rotifers being the main ones, and juveniles prevailing among copepods. In 1999–2001, the average abundance of metazooplankton in the lake was 1570 × 10³ ind m⁻³; in the epilimnion 2320 × 10³ ind m⁻³, in the metalimnion 2178 × 10³ ind m⁻³, and in the hypolimnion 237 × 10³ ind m⁻³. The average biomass of metazooplankton was 1.75 g m⁻³; in the epi-, meta- and hypolimnion, accordingly, 2.16, 2.85 and 0.26 g m⁻³. The highest abundances – 19,136 × 10³ ind m⁻³ and 12,008 × 10³ ind m⁻³ – were registered in the lower half of the metalimnion in 24 May and 5 June 2001, respectively. Rotifer Keratella cochlearis f. typica (Gosse, 1851) was the dominating species in abundance. In biomass, Asplanchna priodonta Gosse, 1850, among the rotifers, and Eudiaptomus graciloides (Lilljeborg, 1888), among the copepods, dominated. According to the data from 2000–2001, the abundance and biomass of both copepods and rotifers were highest in spring. Zooplankton was scarce in the hypolimnion, and no peaks were observed there. During the summers of 1998 and 1999, when thermal stratification was particularly strong, zooplankton was the most abundant in the upper half of the metalimnion, and a distinct peak of biomass occurred in the second fourth of the metalimnion. Probably, the main factors affecting the vertical distribution of zooplankton in L. Verevi are fish, Chaoborus larvae, and chemocline, while food, like phytoplankton, composition and abundance may affect more the seasonal development of zooplankton.     

Food and feeding relationships of young fish in the first weeks after the beginning of exogenous feeding in Lake Opinicon,Ontario

Synopsis Young fish of six species in an open water community all began their exogenous feeding by taking nauplii and small cyclopoids of body length (less tail) of 0.1–0.3 mm. Appearance of larvae of the different species in the system was, however, sequential, the resource being utilized by the different species in turn. The sequence was: Perca flavescens, Percina caprodes, Pomoxis nigromaculatus, Ambloplites rupestris, Lepomisgibbosus and L. macrochirus.The larvae and juveniles changes their diet rapidly as they grew. Fish 10–14 days after hatching and 8–10 mm in length i.e. close to the beginning of the juvenile period, consumed larger-bodied prey items (including several genera of Cladocera) and had more diversified diets than the 4.5–6.0 mm first-feeding larvae. These differences, and progressive dispersal of the larger young from the area, served to minimize the chances of food competition between batches of young of different ages.The composition of the fish community of larvae changed from week to week as new species entered it, increased in size and departed. Patterns of food utilization changed accordingly.Numbers of cyclopoids, their nauplii, and Bosmina longirostris, fell rapidly in May — early June, and did not increase again until August. These changes coincided with the rise and fall in numbers of the young fish in the habitat.Paper presented in the symposium \lsEmbryonic and larval periods of fishes: present status and significance\rs, Canadian Conference for Fisheries Research (CCFFR), Fredricton, New Brunswick, January 1977.     

Seasonal dynamics of the numbers of larvae of common fouling organisms in Balaklava Bay (Black Sea)

The seasonal dynamics of the numbers of larvae of common fouling organisms—the barnacle Balanus improvisus and the bivalves Mytilaster lineatus and Mytilus galloprovincialis in Balaklava Bay (Black Sea)—were investigated during 2000 and 2001 within the framework of an ecological research project. Under the conditions of an increased anthropogenic load, seasonal fluctuations of the numbers and the distribution of larvae depend on rhythms of the breeding cycles of fouling invertebrates and on the hydrodynamic features of the region (water setup). The differences in the optimum temperatures, hatching intensity, and time of occurrence of larvae in the plankton, as well as the irregular distribution of larvae, allow the three major fouling organisms to reduce interspecific competition for food and the substrate.Original Russian Text Copyright © 2004 by Biologiya Morya, Shalaeva, Lisitskaya.     

Crustacean assemblage and environmental characteristics of a man-made solar saltwork in southern France,with emphasis on anostracan (Branchiopoda) population dynamics

Physical and chemical variables, anostracan populations (Artemia parthenogenetica and Branchinella spinosa) and other biota were studied during 1996–1997 in a Camargue saltern (max. depth 1 m). The taxonomic composition and density of macroinvertebrates were investigated twice monthly, based on benthic substrate and water column samples. Fauna was composed of three groups in terms of numerical importance. The benthic macroinvertebrates were represented only by nematodes (< 50 ind. m^–2 to > 500 ind. m^–2 in November–December and May respectively). The zooplankton was dominated by crustaceans, one cladoceran, Moina salina (ranging from 670 to 2350 ind. m^–2 in spring), two anostracans, Artemia parthenogenetica (< 50 ind. m^–2 in autumn), and Branchinella spinosa (max. 190 ind. m^–2 in December to absent in April), and two copepods, Cletocamptus retrogressus (max. density 2000 ind. m^–2 in November), and Eurytemora velox (max. density 650 ind. m^–2 in February–March). Insects (Chironomidae, Culicidae) were rare, with mean densities < 1 ind. m^–2. The phenology of each crustacean population is discussed in relation to physical and chemical water variables. Salinity appeared to be of greatest importance regulating the population abundance.     

Seasonal Dynamics of the Diatoms of the Genus Chaetoceros Ehrenberg in Amursky Bay (Sea of Japan)

The qualitative and quantitative composition of the Chaetoceros Ehr. species was studied in Amursky Bay (Sea of Japan) from January 1996 until May 1998. In all, 30 species, 1 variety, and 1 form of this genus were registered. The species Chaetoceros occurred in plankton throughout the year at a water temperature of –1.8–25°C and a salinity of 11–35. The numbers of Chaetoceros species varied between 100 and 1071000 cells/l, and the biomass varied between 0.9 × 10^–3 and 3.3 g/m³. The numbers were maximum in summer and minimum in the beginning of spring. The Chaetoceros species comprised 45–70 and 5–18% (winter), 68–98 and 65–95% (spring), 50% (summer), and 20% (autumn) of the total phytoplankton numbers and biomass. Six dominant species and 1 variety of Chaetoceros were found. Seasonal complexes formed by the Chaetoceros species were identified and described.     

Feeding and growth of larval herring,Clupea harengus,in relation to density of copepod nauplii

Synopsis Feeding and growth rates of 1–3 wk old herring larvae from four different stocks were compared in laboratory experiments (8°C). For most of the larval groups, feeding rate was saturated at nauplii (Acartia tonsa, nauplii stages 3–5) densities over 301^–1 (5 g d.w. 1^–1). Specific growth rate increased asymptotically with nauplii density, and reached about 6% d^–1 at densities over 120 nauplii 1^–1. The growth rates attained in the laboratory were similar to field measured growth rates of similarly aged herring larvae at comparable food densities. Since food particles were homogenously distributed in the laboratory tanks, patches of dense plankton concentrations are, thus, apparently not necessary for larval growth and survival in the sea. Growth efficiency differed between larval groups, with large sized larvae being the most efficient in transforming ingested matter into growth. The difference probably relates to different sizes rather than to the different geographical origins of the larvae.     

Respiratory metabolism of Hydromedion sparsutum and Perimylops antarcticus (Col., Perimylopidae) from South Georgia

Summary Metabolic rates were studied in adults and larvae of the two phytophagous beetles Hydromedion sparsutum and Perimylops antarcticus (Col., Perimylopidae) indigenous to the Sub-Antarctic island of South Georgia. From the regression lines for log₁₀ metabolic rate on temperature no difference in oxygen consumption was found between adults and larvae of Hydromedion or adults of Perimylops from lower sites near sea level and upper sites at about 200 m. Elevated rates of metabolism, however, was found in larvae of Perimylops from upper sites. The slopes of the regression lines of corresponding upper and lower sites adults or larvae were similar in all cases. The metabolic rates were of the same level in adults of both species and in the larvae, but generally higher in adults than in larvae. The activation energies, calculated from Arrhenius plots, varied from 6.7 to 13.6 kcal.mol^–1 in larvae and from 10.7 to 11.3 kcal.mol^–1 in adults. The low values may be interpreted as an expression of cold adapted metabolism. Compared with published data on phytophagous beetles, the metabolic rates of the two species from South Georgia are comparable to two alpine species, but lower than the rates of an Arctic species.     

Bacterial Population Association with Phytoplankton Cultured in a Bivalve Hatchery

Bacterial populations association with phytoplankton cultures used as food for bivalve larvae were enumerated and identified from their partial 16S rDNA gene sequences. Microalgae were provided from different European hatcheries during the larval production season. Average concentration (direct counts) of bacteria ranged from 1.3 × 10⁵ to 5.3 × 10⁸ mL^–1 while culturable bacteria represented from 10% to >60% of total bacteria. In most cases, three to six representatives of each type of colony were collected on solid medium. The identity of isolates from the same colony type was checked by two different randomly amplified polymorphic DNA (RAPD) typing methods, after which the 16S rDNA gene of one to three isolates by colony type were partially sequenced. Algae harbored a large spectrum of bacteria belonging to the -Proteobacteria, -Proteobacteria, -Proteobacteria, Cytophaga– Flavobacterium– Bacteroides (CFB) group, Actinobacteria, and Bacillus. Members of the Roseobacter clade and CFB group were the most abundant. In the majority of cases one strain constituted 50% or more of the culturable bacterial flora. About half of the isolates were common to two hatcheries or at least two microalgal cultures. Several isolates were closely related to bacteria associated with harmful dinoflagellates in culture. Thus, the algal cultures seemed to favor certain bacterial species which belonged to distantly separated groups. As some of them could disturb the development of bivalve larvae, the control of bacterial populations would undoubtedly make it possible to reduce larval losses in bivalve rearing.     

The Distribution of Bacterio- and Mesozooplankton in the Coastal Waters of the White and Barents Seas

The total population density and the biomass of bacterioplankton, mesozooplankton, and phosphate-accumulating bacteria (PAB) were estimated during the 2000–2001 summer–autumn seasons in the coastal waters of the White and Barents Seas, which are subject to the action of tidal and sea currents, the inflow of riverine waters, and anthropogenic impact. In the shallow estuarine waters with salinities of 6.5–32 near the Chernaya, Pesha, and Pechora River mouths, the population of PAB fluctuated from 0.1 to 9.1 million cells/ml (0–36% of the total bacterial population). In pelagic seawaters, which are low in phosphates (12–50 g/l) and are characterized by an increased iron/phosphorus ratio (2.0–3.6), bacterioplankton amounted to 0.1–1.6 million cells/ml and was mainly represented by small organisms with a volume of 0.08–0.15 m³, commonly lacking intracellular polyphosphates. In the pelagic zone of the Barents Sea, the biomass of mesozooplankton (B _z) was comparable with that of bacterioplankton (B _b = 39–175 mg/m³), the B _b/B _z ratio being 1.4–4.6. Off the Varandeiskii, Pechora, and Kolguyev oil terminals, B _b increased to 155–300 mg/m³ and the B _b/B _z ratio rose to 1.4 to 50.3 (with an average value of 20.9), presumably due to the severe anthropogenic impact on these waters. In this case, the dense population of bacterioplankton (0.9–7.6 million cells/ml) was mainly represented by large cells (0.12–0.76 m³ in volume), most of which (3–43% of the total bacterioplankton population) contained polyphosphates. The chemical composition of these waters was characterized by an elevated content of the total phosphorus (65–128 g/l) and by a low iron/phosphorus ratio (0.9–1.2).     

Feeding by larvae of Hypoatherina tropicalis (Pisces: Atherinidae) and its relation to prey availability in One Tree Lagoon,Great Barrier Reef,Australia

Synopsis Feeding of and food availability for larvae of Hypoatherina tropicalis were investigated in One Tree Lagoon, Great Barrier Reef, Australia, during November 1981 and January 1982. These surface-dwelling larvae and their microzooplankton prey were sampled as near to simultaneously as possible on 12 occasions during the daytime. Larvae of all sizes (5–17 mm SL) fed successfully over the observed range of mean prey densities (12–235 per liter), and the overall feeding incidence was 98.9%. Larger larvae consumed greater numbers and more categories of prey than did smaller larvae. Larvae selected copepods of all sizes, and nauplii, gastropods, bivalves, and foraminiferans that were greater than 75 ¢s mm in width. Tintinnids (mostly 37–74 µm in width) were generally avoided by larvae, but were occasionally important in the diets when they constituted more than 60% of the total available prey, regardless of the density of the selected prey categories. Larvae less than 14 mm SL ingested meroplankton (gastropods, bivalves, foraminiferans, and polychaetes) in direct relation to the densities available, and without regard to the densities of copepods available. However, the largest larvae (14–17 mm SL) ingested meroplankton in inverse relation to the density of copepods available, indicating that larvae consumed more meroplankton when the concentration of copepods was low. Such flexibility and opportunism in feeding behavior may increase the larvae's chances of obtaining adequate nutrition during periods of suboptimal feeding conditions.