Abundance Of Polychaetes Research Articles

Structure and temporal dynamics of macroinfaunal communities of a sandy reef flat in the northwestern Philippines

Temporal variation in macroinfaunal community structure wasassessed from monthly monitoring of the sandy substrate of theLucero reef flat in Bolinao, Pangasinan (northwesternPhilippines)between November 1990 and November 1991. The community wascomposedof 98 taxa from 10 phyla and was consistently dominated by thepolychaete family Syllidae (19–33% of monthly totalabundance).Five polychaete and crustacean taxa co-dominated with thesyllidsand exhibited monthly shifts in dominance ranks. Overall,there wasno significant change in the composition of the communityafter ayear.Results of the study show that the temporal dynamics of thecommunity was a function of the seasonality in salinity and oftherelatively consistent nature of the substrate. Abundances ofmacroinfaunal crustaceans, chaetognaths, and molluscsfluctuatedsignificantly over 12 months, and corresponded to the seasonalfluctuation in salinity. Total and polychaete abundances didnotshow significant monthly variation, but tended to beinfluenced bysalinity changes. Densities of turbellarians, nemerteans, andechinoderms appeared homogeneous across 12 months, andcorrelatedwith the consistency of substrate structure in the reef flatoverthe experimental period. In addition, sipunculid numbersseemed tobe supported by the stable amount of organic matter in thesandysubstrate.

Size-dependent, small-scale dispersion of the capitellid polychaete, <I>Mediomastus ambiseta</I>

Small(∼cm)-scale spatial pattern of an abundant capitellid polychaete, Mediomastus ambiseta Hartman, was investigated in sediments of central Narragansett Bay, Rhode Island, USA from fall 1988 through spring 1992. Spatial autocorrelation techniques revealed a trend of decreasing patchiness and intensity of aggregation with increasing body size of M. ambiseta during the primary period of settlement and population growth (late summer-fall). The distribution and quality of particulate organic matter may explain the observed size-dependent spatial pattern. M. ambiseta influenced the small-scale distribution and concentration of organic matter and bacteria in surficial sediment. Experiments and field studies showed that this species creates two distinct sediment habitats through its sediment reworking activities: a surface pelletized zone enriched in organic matter and depleted in bacteria, and an underlying 'feeding' zone depleted in organic matter. Within the feeding zone of M. ambiseta in field-collected sediments, bacterial growth was enhanced. A density-dependent growth experiment suggested that small-scale aggregation in M. ambiseta may occur at the expense of individual growth.

The effect of Manila clam cultivation on an intertidal benthic community: the early cultivation phase

With increasing awareness of the use of the coastal zone, it is necessary to understand the potential environmental effects of aquaculture practices. This is especially important when non-native species, which may be competitively superior to native species, are cultivated. A 5-year experiment was established to study the environmental effects of the various stages of Manila clam. Tapes philippinarum Adams & Reeve, cultivation, from seeding, through on-growing, harvesting and post-harvesting. The aim was to monitor changes in biological and physical variables in the sediment which may be useful in formulating an environmental management strategy for the cultivation of this species. This paper describes the biological and physical changes that occur in the sediment during the early phase of clam cultivation. We compared the changes in netted plots (with and without clams) and unnetted control areas, 6 months before and after laying the clams. The clams were planted in April 1992 under netting at a density of 500 m-2 (0.16 kg m-2), and in 6 months, had increased their weight to 3.2 kg m-2 but decreased their number to 410 m-2. A significant, but small increase in organic content (net only plots, 3.37%; control plots 2.42%) and in phaeopigment (netted plots, 8.6 mg m-2; control, 5.6 mg m-2) of the sediment in the netted plots relative to the control areas were seen. Short-term sedimentation rates on the netted plots were up to four times higher than in the control areas. The netting also encouraged the settlement of Enteromorpha sp. which, in turn, attracted Littorina littorea to feed on these plots. The infaunal community in the control areas was similar to that in samples 12 months earlier and continued to be dominated by the predatory polychaete Nephtys hombergii. Netted plots (with and without clams) had a greater abundance of deposit feeding polychaetes. particularly Ampharete acutifrons and Pygospio elegans, which were the dominant fauna in these plots. Within the clam treatments, the density of clams had a negative effect on the abundance of cirratulids, although mean abundance was generally greater than in the control areas. There were few physical changes to the experimental area after 6 months. The most important effect appears to be the increased sedimentation rate over plots with netting, which has led to an increase in productivity of those areas.

Grazing by meroplanktonic polychaete larvae may help to control nanoplankton in the NW Mediterranean littoral:in situ experimental evidence

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 143:239-246 (1996) - doi:10.3354/meps143239 Grazing by meroplanktonic polychaete larvae may help to control nanoplankton in the NW Mediterranean littoral: in situ experimental evidence Martin D, Pinedo S, Sardá R In this paper, we test the potential meroplankton grazing pressure on the nanoplanktonic community at the Bay of Blanes (NW Mediterranean). We used 2 abundant polychaete larvae (Prionospio malmgreni and Loimia medusa) cultured in situ in dialysis bags from which possible nanoplankton grazers other than larvae had been removed by filtration.Ingestion rates on chlorophyll a ranged from 0.001 to 0.04 and from 0.045 to 0.117 µg larva-1 d-1 for P. malmgreni and L. medusa, respectively. Ingestion rates on heterotrophic nanoflagellates (HNF) ranged from 2.4 to 32.3 x 103 and from 20.8 to 128.0 x 103 cells larva-1 d-1 for P. malmgreni and L. medusa, respectively. Scaling larval grazing to the natural plankton community results in: (1) a consumption on nanophytoplankton production ranging between 2.5 and 7.0%, corresponding to percentages of nanophytoplankton loss in ambient waters of 2.3 to 6.4%, respectively; (2) a consumption on HNF production ranging between 3.1 and 12.4%, corresponding to percentages of HNF loss in ambient waters of 2.9 to 11.7%, respectively. Although limited in time, the presence of planktotrophic larvae could cause an impact on nanophytoplankton populations which could be of similar relevance to that of holoplanktonic grazers, at least in shallow littoral waters of the Mediterranean Sea. Although potentially high, the estimated ingestion of nanophytoplankton by polychaete larvae was not sufficient to explain the major losses observed in the field, suggesting that these losses must be a result of consumption by other zooplanktonic grazers as well, and/or from processes other than herbivory. Contrary to nanophytoplankton and HNF, bacteria showed enhanced abundance in the presence of both polychaete larvae. Grazing by polychaete larvae caused a disruption of the grazing control exerted by HNF on bacteria. In conclusion, our results strongly indicate an important trophic role of meroplankton both as a direct control of the microbial holoplanktonic populations, and as a source of cascading effects in the microbial planktonic food webs. Meroplankton · Polychaete larvae · Grazing · Nanoplankton control · NW Mediterranean Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 143. Publication date: November 14, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Resident Fishes and Macrobenthos in Mangrove-Rimmed Habitats: Evaluation of Habitat Restoration by Hydrologic Modification

An impounded area (Cabbagehead Bayou) in Upper Tampa Bay, Florida, was studied for 13 mo prior to and 22 mo after berm removal. Sampling for small fish and macrobenthos was conducted both at Cabbagehead Bayou and at a nearby control site, Double Branch Bay. Before and After Control and Impact (BACI) analyses, as well as similarity indices, were used to evaluate faunal characteristics in control versus impacted areas. Berm removal drastically changed periodicity of water cover in the impacted site, with the previously impounded site becoming almost entirely exposed during low tide. Fish abundances, biomass, and mean monthly number of species decreased in Cabbagehead Bayou after tidal flow was established as compared to when it was impounded. Responses of macrofauna varied among taxa, but total amphipod and polychaete abundance displayed a relative increase in the impacted site after berm removal. BACI analyses indicated that the relationship between mean values for almost all polychaete and amphipod taxa in the impacted and control sites changed significantly after berm removal. Additional differences were apparent in BACI analyses, which showed a significant change in the relationship of fish abundance and biomass at both sites for prebreach vs post-breach samples. The changes in relationships were generally not indicative of convergence of control and impacted sites, however. Community similarity of fish, amphipod, and polychaete assemblages increased during the last year of the post-breach sampling but remained generally very low. These findings suggest that distinct faunal responses to alteration of tidal periodicity can be detected within less than 2 yr after reestablishment of tidal flow. However, attainment of close correspondence to control conditions for certain fauna may require more than 22 mo. Therefore, future studies attempting to document recovery of restored wetlands may benefit from extended duration.

Observations on the biota of an estuarine beach at Hardys Bay (NSW, Australia) following a spillage of aldrin

An industrial accident resulted in a spillage of aldrin onto an estuarine beach at Hardys Bay, New South Wales. Samples of water and sediment were taken 3 weeks later to measure the level of contamination resulting from the spill. The abundances of some intertidal biota were also determined at the site of the spillage and in other uncontaminated areas. Three weeks after the spill, samples of water were not contaminated by aldrin but samples of sediment from the surface in the vicinity of the drain contained aldrin. In comparison to uncontaminated locations the abundances of crustacea were greatly reduced in the vicinity of the drain but abundances of polychaetes were not significantly different. The field data on the relative susceptibility of the two groups of animals agrees well with laboratory derived LC50 data for crustacea and polychaetes. The study suggests that degree of contamination of water and sediment may not always be an accurate reflection of acute impact on biota, and that different components of the biota can show different reactions to the presence of a toxic chemical.

Polychaetes of the shallow sublittoral of Admiralty Bay, King George Island, South Shetland Islands

Twenty five species of Polychaeta were recorded in soft bottom samples collected from 4–30 m. Total abundance of polychaetes ranged from 60 to 3300 m-2. High abundance values were locally recorded for Microspio moorei, Tharyx epitoca and Ophelina syringopyge. These species, together with more regularly distributed Capitella capitata and Scoloplos marginatus, constituted over 70% of all specimens. Total biomass value of the polychaetes varied between 3.8 and 46.4 gm-2. Travisia kerguelenensis and Aglaophamus ornatus constituted over 75% of total biomass. Species composition, richness and diversity of the polychaete assemblage varied with depth. Two parts of the investigated bottom section, differing in the polychaete assemblages structure, were distinguished; the first one in the depth range from 4–20 m and the second one at the depths of 25–30 m. On the basis of both new and previously published data two types of polychaete assemblages of the shallow soft bottom of the Antarctic sublittoral were distinguished. The type of sediment seems to be the main factor influencing the composition of polychaete assemblages.

Distribution of antarctic zooplankton around Elephant Island during the austral summers of 1988, 1989, and 1990

Year to year variation and vertical distributions of epipelagic Zooplankton around Elephant Island and King George Island were examined with samples collected with bongo nets and a 1 m2 MOCNESS during the austral summers (Jan–Feb.) of 1988, 1989 and 1990. Copepods were the major components of epipelagic Zooplankton (in numbers) with dominance of Metridia gerlachei (1988 and 1989) and small calanoids and cyclopoids (1990). Euphausiids and salps were the next most abundant groups. The percent composition of euphausiids decreased from 1988 to 1990 while that of salps increased. The abundance of salps exceeded euphausiids and major taxa of copepods in 1990. Local patches of polychaetes and amphipods were also found. Statistically significant annual variations with increased numbers in 1990 were found by analyses of variance in total abundance, abundances of copepods, salps, chaetognaths and amphipods, but abundances of euphausiids, polychaetes and fishes showed no significant annual variations. When the study area was divided geographically, horizontal variability in abundance within each year showed no significance in total abundance, abundances of copepods, euphausiids, amphipods and fishes, but significance in salps, polychaetes and chaetognaths. Results of site clustering based on covariances of abundances of eleven major taxa were well matched, though not perfect, with the distribution of surface water temperatures which could be used as a tracer of source water masses suggesting that spatial variation was related to hydrodynamic conditions. Factor analyses showed that annual and spatial variations in abundance were mainly caused by only two taxa, Metridia gerlachei and salps (mostly Salpa thompsoni). These two taxa were responsible for about 60% and 30% of total variance, respectively, and were useful indicators of the interannual variation. That is, 1988 and 1989 were the years of M. gerlachei, and 1990 was the year of salps. From vertically stratified MOCNESS samples, it was shown that the major taxa in this study area were active vertical migrators. While most samples obtained by relatively shallow tows (uppermost 100 m depth) were composed of exclusively one or two taxa, those from relatively deep tows (down to 200 m) showed various patterns of vertical stratification suggesting that the patterns of vertical migration were species specific. Species specific ontogenetic vertical migration associated with elevated habitat temperatures also seemed to be responsible for the annual variation in zooplankton distribution in the upper water column.

Do toxic algal blooms affect subtidal soft-bottom communities?

An extensive bloom of the toxic flagellate Chrysochromuha polylepjs occurred over much of the Skagerrak and Kattegat area during May-June 1988 with severe effects on biota in shallow marine habitats. Results reported here are from annual grab-sampling of subtidal soft-bottom communities off the southwest coast of Norway during the period 1986 to 1991 at depths between 69 and 184 m, and describe changes In fauna associated with the toxic algal bloom. In the 3 years prior to the bloom the fauna at each station was persistent and only modest year-to-year changes in the number of species, abundance and species composition were observed. Samples collected 1 yr after the bloom event revealed a significant reduction in both number of species and individuals. The most obvious changes were found at sites situated in accumulation areas characterised by fine sediments indicating a possible connection between the quantity of sinking toxic material and the degree of faunal perturbation. A DCA ordination demonstrated a clear switch in faunal composition in the study area subsequent to the bloom, and a tendency of the fauna to return to the pre-bloom communities 2 yr after the bloom event. Principal species affected were moderately abundant oligochaetes, polychaetes, crustaceans, molluscs and sipunculids. Allocation of each species into the categories 'gaining' and 'losing' according to annual changes in abundance gave a good description of the community disturbance probably induced by the toxic alga. Other possible causes for the observed faunal perturbation may be changes in water temperature, food input, predation interference and changes in sediment composition, but none of these were found to give reliable, alternative explanations for the substantial changes observed in the soft-bottom communities subsequent to the toxic bloom.

Predation effect of three fish species and a shrimp on macrobenthos and meiobenthos in microcosms

The responses of macrofaunal and meiofaunal benthic communities to predation by three fish species and a penaeid shrimp were examined to evaluate the potential for epibenthic predators to reduce abundance of benthos. Experiments conducted in 1987 analysed only the macrofaunal community and indicated capitellid polychaete abundance was significantly reduced in the presence of white shrimp [ Penaeus setiferus (Linneaus)], while mummichogs [ Fundulus heteroclitus (Linneaus)] had no significant effect on any macrobenthic taxon. Experiments in 1988 using mullet ( Mugil cephalus Linneaus) as predators resulted in significantly decreased abundances of total meiofauna and the copepod Enhydrosoma propinquum (Brady), while abundances of macrofaunal prey were not significantly reduced. Abundances of the polychaete Streblospio benedicti Webster, total macrofauna and total copepods were significantly reduced by spot ( Leiostomus xanthurus Lacepede) predation. While these experiments were designed with sufficient power to demonstrate that epibenthic predators are possibly capable of causing significant reductions in the populations of macrofaunal and meiofaunal prey, a general paucity of significant impacts indicates that these predators may be but one of many factors influencing benthic abundance in the field. The microcosm experiment approach must incorporate multifactorial designs in the future.

Monitoring the shallow sublittoral using the fauna of kelp ( Ecklonia radiata) holdfasts

The macrofaunal community inhabiting the holdfast of the kelp, Ecklonia radiata, was assessed for changes along a putative gradient resulting from an outfall of low volume domestic effluent. Multi-dimensional scaling (MDS) revealed a consistent separation of treatment sites from controls at each of the three sample periods. Changes in trophic structure were dectected as well as shifts in relative abundances of amphipods and polychaetes as measured by the amphipod to polychaete ratio. Data were further analysed using the Ewens-Caswell neutral model which proved a useful tool for detecting differences between samples from control and treatment locations.

The fauna of the HEBBLE site: patterns in standing stock and sediment-dynamic effects

At the High Energy Benthic Boundary Layer Experiment (HEBBLE) site at 4820 m depth on the Nova Scotia Rise (40°27′N, 62°20′W), abundances of polychaetes, bivalves, tanaids, and isopods were conspicuously greater than expected for the depth, whereas those of nematodes and harpacticoids, the two dominant meiofaunal taxa, were not. Further, the abundances of polychaetes, bivalves, tanaids, and nematodes were consistent over time and appeared to be unaffected by the periods of strong near-bottom flow that characterized the site. In contrast, isopods and harpacticoid copepods were less abundant in samples taken as a storm abated, apparently because they were eroded during benthic storms. We explore implications of the difference between macrofaunal and meiofaunal abundance for community structure. In addition, because a goal of the HEBBLE project was the parameterization of sediment transport in the deep sea, we summarize ways that the biota affects sediment transport at this high-energy site.

Experimental Studies of Predation on Polychaetes Associated with Seagrass Beds

Predation on benthic polychaetes associated with seagrass beds was examined in laboratory and field predator inclusion experiments with one fish and three invertebrate predators. Predation had differential effects on polychaete taxa which depended on their microhabitat utilization patterns. The magnitude of predation effects strongly depended on the predator species, with the shrimpPenaeus duorarum having the greatest impact and the pinfishLagodon rhomboides the least. Abundance of spionid polychaetes, which are located near the sediment-water interface, was reduced most often by predation. Nereid and capitellid polychaete abundances were reduced by some predators and not by others. The results emphasize the need for more detailed natural history information on polychaete species in order to improve the interpretation of results from predation experiments.

Historical changes in the benthos of the Wadden Sea around the island of Sylt in the North Sea

The situation regarding the distribution and abundance of seagrass, macroalgae and benthic fauna near the island of Sylt in the south-eastern North Sea during the period 1923 to 1940 is compared with that of the 1980s. Evidence of organic enrichment in recent times is provided by (1) massive growth of green algal mats on sheltered tidal flats, (2) a decline of red algae in the subtidal zone, (3) an expansion of mussel beds along low water line and down to 20 m depth, (4) increased abundance of polychaetes inhabiting intertidal and subtidal sandy bottoms. Seagrass beds have undergone complex changes which remain unexplained. Intensified erosion has contributed to the loss of habitats in the intertidal zone, and probably affected sessile epifauna in the deep channels. Here, direct removal and disturbance by the bottom-trawling fishery may also have contributed to the observed species impoverishment.

Estuarine Macrobenthos in Calcasieu Lake, Louisiana: Community and Trophic Structure

Macrobenthic assemblages in Calcasieu Lake estuary (Louisiana) were sampled at 11 sites from October 1983 through November 1985. The sites were numerically dominated by subsurface-deposit feeders, consisting mostly of polychaetes. Greater densities of macrofauna were collected at the northern (upper) stations of the lake than were collected in West Cove or the southern stations. Abundances of polychaetes, oligochaetes, and amphipods at the upper lake stations accounted for most of the differences among stations. The numerical dominance by detritivores (97% of the fauna) and lack of strong sediment or salinity gradients across the estuary, resulted in an absence of temporal pattern in trophic structure of the macrofauna.

Deep‐Sea Polychaetous Annelida from Central America to the Antarctic Peninsula and South Sandwich Islands

AbstractBased on the 1958 Vema cruise and the 1965 Anton Bruun cruise 11 off the west coast of Central America and south through the islands east of the tip of South America, 143 trawl samples were examined for abyssal polychaetous annelida. The cruise tracks designated 7 major areas: Central America (1), Ecuador‐Peru (II), Central and Southern Chile (III), Chile and the Magellan Strait (IV), Tierra del Fuego (V), the Island Complex (Falkland, South Georgia and South Sandwich Islands) (VI), the Drake Strait and Antarctic Peninsula (VII). The collections yielded 7,015 individuals and 322 species from 52 families. The relatively small number of species was attributed mainly to sampling effort, collecting gear and processing techniques.Each major area was characterized in terms of the number of individuals, the number of species, mean number of individuals, mean number of species and mean H′, SR, J′ and DI. Species diversity was significantly higher in Central America (I) than in the other areas. The relationships between biotic and abiotic measures (depth and areas of upwelling) were examined. There were no significant associations for the entire data base with depth. Moreover, there was no association between abundance of polychaetes and areas of upwelling which was hypothesized. In fact, relative abundance was highest in the deepest portions of Central America (I) (Guatemala Basin) and Ecuador—Peru (II) (Milne—Edwards Deep) compared to shallower areas closer to areas of upwelling. Quantitative collecting gear and refined processing techniques will be required to more accurately address these relationships.Dominant families were identified in terms of number of species and number of individuals. These families conformed well with world wide generalizations of dominant families. Dominant species were identified based on the Biological Index Value. The top twenty or dominant species for each major area were identified. A number of these dominant species occurred widely throughout the major areas. The dominant species for the entire data set were determined. In general these species were very eurybathic which was consistent with other worldwide depth distributions of abyssal polychaetes.Based on biotic measures (mean number of species, mean H', SR, J′ and DI) and the Simpson and Dice similarity co‐efficients, several zoogeographic patterns emerged. The polychaete fauna from Central America (I) to southern Chile (II) formed a relatively homogeneous group. Polychaetes from Central America (I) had affinities with faunas studied off western Mexiko. The Chile and Magellan Strait (IV) area seemed to be a transition area which yielded to another relatively homogeneous fauna comprising areas V—VII. The latter fauna belonged to an Antarctic polychaete fauna which was documented earlier in other studies with a larger data base and more sophisticated analysis. It is hoped that the present study will help to provide a start to fill the zoogeographic gap of this enormous and bathymetrically diverse area.

Long-term structure, disturbance, and recolonization of macroinfauna in a New Hampshire sand beach

The southern portion of Foss Beach, New Hampshire, was totally eroded of sand during the second quarter of 1977. Long-term community data from the beach since 1971 served as background for studying recolonization by burrowing invertebrates after redeposition of sand. About 2 years were required for the beach to regain much of its sand, and another year passed before a complete coverage of sand was long lasting. Twenty-five species of macroinfauna were recorded from the beach during a 13-year period, seven of these only from the postdisturbance beach. The polychaetes Scolelepis squamata and Paraonis fulgens, and the amphipods Acanthohaustorius millsi and Amphiporeia virginiana, were the most abundant species. The numbers of species and abundances of polychaetes were the primary influences on the pattern of variation of the total macroinfauna before disturbance. Polychaetes also dominated during early recolonization, 1.5–2 years after sand erosion, particularly species with planktonic larval stages. During this time, Capitella sp. exhibited abundances up to 10 times mean values for the predisturbance period. Four years after sand erosion, the macroinfauna had largely recovered.

Patterns of polychaete recolonization in Queensland subtropical estuaries following severe flooding

Quantitative sampling of macrobenthos and fouling organisms in the estuarine reaches of the Calliope River and Auckland Creek, Gladstone, Australia has been conducted since November 1974, and includes the recovery period (1974–1981) following severe flooding (and flood-induced scouring) in December 1973/January 1974. Changes in numbers of the 18 most abundant species of benthic polychaetes and one encrusting serpulid (Ficopomatus uschakovi) are examined. Numbers of F. uschakovi settling on fouling panels showed a regular seasonal pattern, with a late summer maximum and a winter minimum throughout this period. The total numbers of individuals for all taxa in benthic samples followed a clear colonization pattern, with super-imposed seasonality; plateau densities were reached five years after flooding. Total numbers of the 18 most abundant polychaetes showed a similar recolonizational pattern including the seasonal variation.

陸奥湾におけるマクロベントスの時空間分布

In order to elucidate the conditions of food environments for righteye flounders Limanda herzensteini and L. yokohamae in Mutsu Bay, Aomori Prefecture, the distributions of macrobenthos were investigated by analyzing grab samples obtained at approximately 300 stations chiefly from March 1980 to February 1983. Faunal composition in the bay was correlated with the mud contents in the bottom sediments. In the extensive mud bottom in offshore area polychaete annelids predominated, representing 82.8% of the total number of macrofauna. Most of the dominant species, Scalibregma inflatum, Paraprionospio pinnata, and Maldane sarsi, were chiefly abundant in East Bay. So macrofaunal biomass and density in West Bay were consistently lower than those in East Bay. The densities of S. inflatum and Ampharete sp. increased remarkably in spring and decreased in autumn and winter, while no seasonal periodicity was found in fluctuations in den-cities of Lumbrineridae and M. sarsi. There is a general tendency that the macrofaunal biomass in offshore area attains peak in summer and lowest in winter. But such a periodicity was not found in East Bay since the autumn of 1980 because of remarkable increase in density of M. sarsi. Results of cluster analysis showed that the community structure of macrofauna in offshore area varied largely with fluctuations in abundance of dominant polychaetes by seasons and years.

Jaw Mineralogy in Eunicean Polychaetes (Annelida)

X-ray diffraction analysis of jaws from representatives of five families of eunicean polychaetes indicates that three different types of mineralization are represented. Aragonite is reported for the first time from species within the families Onuphidae and Eunicidae. Jaws of species in the Lumbrineridae are mineralized with calcite, as are those of Lysarete. Other lysaretids and members of the Arabellidae have jaws which are amorphous to X-rays, as are those of the unrelated glycerids and nereidids. In combination with other morphological characters, the mineralogy of the jaws is a useful taxonomic character within the superfamily Eunicea at the family level. The calcified jaws and those of the nereidids are weakly sclerotized, and may have relatively low fossilization potential. This may explain the relative rarity of polychaete jaws in post-Devonian rocks in contrast to the abundance of jawed polychaetes in the modern oceans.-Author