摘要:

Abstract.Recruitment of demosponges(Porifera, Demospongiae)was monitored bimonthly for one year (March 1987 – March 1988) on acrylic plates, and compared to cover of adults, in six rocky and coral reef habitats at Santa Marta, Colombian Caribbean, an area subjected to seasonal, upwelling‐outwelling regimes. According to suggestive but not significant trends, recruitment rates are more positively influenced by the total sponge cover near groups of plates than by cover at a larger (habitat) scale; recruit mortality is lower where recruitment is higher. These findings are in agreement with a model of higher settlement (probably due to short‐distance dispersal) and lower postsettlement mortality within a few meters of adult sponges. Recruitment varied seasonally, being relatively high from May to November‐December during the rainy, outwelling season, when seawater temperature was warmer, water turbidity higher, and benthic algal density lower; it was very low from January to April during the dry, upwelling

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1993.tb00361.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.The ecology of tropicalMysidaceais poorly known.Mysidium columbiae(Zimmer), because of its ubiquitous distribution in the tropical western Atlantic and the information available on its aggregative behavior, is an ideal subject of study to reconcile aspects of this problem. Information and data were obtained on abundance, population size, shoal/school structure, fecundity, development, and feeding of aM. columbiaepopulation inhabiting waters surrounding Twin Cays, a mangrove archipelago in Belize. Although reproduction was continuous and proportions of life stages within shoals remained relatively constant throughout the year, population size decreased by an order of magnitude from summer to winter. Embryonic development averaged 4.7 days, with postlarvae being released near the surface before dawn. Aquarium experiments suggested that olfaction may be more sensitive than vision, although both senses were used to locate food. This species is a detritivore, but gut contents suggested that it may also be a predator.

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1993.tb00362.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Biological zonation in brackish habitats is usually related to the gradients of several factors, of which salinity is often taken as the most important. In contrast, recent papers, mainly on Mediterranean lagoons, have emphasized the role of other factors such as water movement and trophic status. In this paper, the distribution of polychaetes in the Orbetello lagoon (a poly‐hyperhaline pond on the northern Tyrrhenian coast) is compared with the gradients of a number of environmental parameters. Polychaete distribution turned out to be under the control of a variety of highly interrelated factors. The study of biotic zonation as a function of a single driving factor is thus overly simplistic even when dealing with ‘simple’ environments, as lagoons are often defined. Several factors and their synergistic effects must always be taken into account.SummaryA total of 79 species was collected from 13 sites in the Orbetello lagoon, comprising both brackish‐water and marine species as well as a large number of species typical of organically enriched habitats. Through correspondence analysis, three major polychaete assemblages were recognized, linked to three different zones of the lagoon: 1) the channels connecting the lagoon to the sea; 2) the western lagoon; 3) the eastern lagoon (including a small part of the western lagoon situated near the town of Orbetello). Such a zonation was shown ‐ by Trend Surface and linear correlation analyses ‐ to be consistent with the spatial trends of a number of environmental parameters such as vivification/confinement, water movement, dissolved oxygen, poikilohalinity, and poikilothermy (in the order of importance); in contrast, salinity (minimal values), sediment grain size, and primary productivity showed little or no relation to polychaete distribution. However, almost all environmental parameters were significantly correlated with each other, thus making it impossible to identify the principal factor. This demonstrates that biotic zonation cannot be explained as the resultant of the action of a single driving factor (e. g., salinity or confinement), even in environments which are usually considered to be relatively simple from a synecological point of view, such as brackish habitats. Both the synergism among the various abiotic factors and the influence of biotic interactions must always be taken i

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1993.tb00363.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Oviparous solitary ascidians, such asCiona intestinalis(L.), generally spawn freely into the water‐column where the eggs are fertilized and develop into free‐swimming non‐feeding larvae. In the laboratory, both spawning and settlement are controlled by light. It has been suggested that both spawning and development time are synchronized so that larval settlement takes place under optimal light conditions in the middle of the day when larvae are best able to locate shaded habitats. Our observations of field populations, however, have shown thatCionamay spawn and settle at any time of the day. Freely spawned eggs, which are negatively buoyant and slightly adhesive, may become attached to any available substratum. Ova can also be released in mucus strings which are particularly adhesive and will readily adhere to adultCionaand other surfaces. In all cases, fertilization and development proceed normally. Laboratory investigations have shown that newly hatched larvae may either escape to the plankton or be retained in the mucus string until settlement. Thus, the dense aggregations of both adults and newly settledCionawhich are commonly observed in the field could be explained by abbreviated dispersal due to mucus string spawning and epibenthic retention of eggs.SummaryIn the field,Ciona intestinalisembryos at different developmental stages are found simultaneously, indicating that spawning is not confined to a specific time of day. Free eggs are negatively buoyant and slightly adhesive. Eggs are spawned in mucus strings, where fertilization and development takes place. Such strings are retained epibenthically. Settlement and subsequent metamorphosis takes place in the mucus strings, but in the laboratory 40 to 60 % of the larvae escape to the plankton. The aggregation of both adult and juvenileCionaobserved in the field can be explained by mucus string spawning and epibenthic retention of

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1993.tb00364.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.To study the impact of the gradient of primary production between the southern, central, and northern Red Sea, benthic metabolism and standing stocks were investigated in the axial trough between 17°N and 27°N. Data on sediment chloroplastic pigments, macrofauna and meiofauna abundance, particulate adenylate, protein and carbohydrate biomass, as well as electron transport activity of the sediment community give evidence for an enhanced benthic standing stock and activity in the southern Red Sea south of 18°N; this is related to the increased primary productivity in the area south 16°N. Despite a large primary production only small benthic standing stocks were found in all areas investigated; they are much smaller than in other parts of the world's deep oceans with comparable primary production. The low benthic biomass is caused by two factors: a large proportion of particulate organic carbon is remineralized in the water column, while only a relatively small amount sediments to the sea floor; nearly all sedimented particulate organic matter is respired by the benthic community of the deep Red Sea and only a minute proportion is used for the production of benthic biomass.SummaryEuphotic zone primary production in the Red Sea decreases in a strong gradient from south to north. Highest primary production occurs south of 16°N. Benthic stocks of the Red Sea axial trough from 17°N to 27°N (water depth ≤ 1000 m), depending on the sedimentation rate of particulate organic matter from the euphotic zone, exhibited a corresponding south to north decrease in macro‐ and meiofauna abundance, biomass (particulate total adenylates, proteins, carbohydrates) and activity (ETS‐activity). All data give evidence for an enhanced benthic standing stock and metabolic activity south of 18°N. In contrast to other subtropical regions with comparable surface primary production, the biomass of the Red Sea benthos appears extremely low. This is caused by two factors: a large proportion of the sedimenting particulate organic matter is already remineralized in the water column, while only a small part reaches the sea floor; nearly all sedimented material is respired by the benthic community and only a minute proportion is channelled into bioma

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1993.tb00365.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Abstract.Two distinctive patterns of microbial destruction of mineral shell in mussels from the Florida Escarpment (3266 m water depth) are described. One pattern follows a surfacial selective removal of intercrystalline organic matrix creating caries‐like pits. Pitting of the shell resembles spreading bacterial colonies and results in substantial thinning of the original shell. The second pattern consists of an extensive system of sacs with branched and tapered extensions penetrating deep into the shell. Both activities are carried out by unknown microbial agents on live mussels, as evidenced by the presence of repair nacre, which often underlies effected areas. Shell destruction is primarily biological, providing conditions for enhanced chemical dissolution of the mineral shell.SummaryDamage and removal of the protective periostracum layer of deep‐sea mussels by various eukaryotic and prokaryotic microorganisms (Hook&Golubic, 1988, 1990, 1992) exposes the mineral portion of the shell to microbial destruction. This biogenic destruction exceeds the rates of inorganic carbonate dissolution in the area of study. Two types of destructive agents attack the shells of live mussels. The first type forms shallow caries along the interface between periostracum and the mineral shell, primarily attacking intercrystalline organic matrix. The second type represents boring microorganisms, morphologically similar to chytrids, that penetrate and permeate the entire mineral portion of the shell. These activities significantly weaken the shell structure and increase its internal poros

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1993.tb00366.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1993.tb00367.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

ISSN:0173-9565    

DOI:10.1111/j.1439-0485.1993.tb00368.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY