Effects of laughing gull and shorebird predation on the intertidal fauna at Cape May,New Jersey

The intertidal flats of the Cape May, New Jersey shore of Delaware Bay are populated by large numbers of laughing gulls and migrating shorebirds during the spring and early summer. Exclusion of birds from a shallow slough and a sand bar had only minor effects on the infaunal benthic invertebrate assemblage at either site. The Cape May beaches provide a rich source of food in the form of horseshoe crab (Limulus polyphemus) eggs; foraging on this item may be more profitable than probing the sediment for infauna. Gemma gemma, a small, thick-shelled bivalve, composed over 98% of the benthic infauna at both sites in 1980, and this species may be resistant to predation by certain shorebirds, as suggested by Schneider (1978).     

The Epibiotic and Endolithic Species Associated with the Gastropod Shells inhabited by the Hermit Crabs Paguristes Oculatus and Pagurus Cuanensis

Abstract. Over 120 species, including epizoites, endolithic organisms, and an epiflora are associated with the gastropod shells inhabited by the hermit crabs Paguristes oculatus and Pagurus cuanensis in the North Adriatic Sea (Gulf of Trieste). The symbiotic organisms include members of three trophic levels - primary producers (rhodophytes), primary consumers (active and passive filter feeders), and secondary consumers (carnivorous species). Many of the invertebrates show a preferred distribution on the shells. The shells are a mobile substratum for a specific community. They are a sediment- and predator-free surface, and for their size are extremely stable substrates in terms of both time and orientation.
The hermit crab microbiocoenosis is a dynamic phenomenon that can be studied as a functional unit. The symbionts are responsible for two simultaneous processes - a constructive and a destructive process on the shells. Shell deterioration is due primarily to biological processes, not to mechanical destruction. The more frequently occurring species were classified according to their role in reinforcing or weakening shell structure. These developments are related to hermit crab activity. Epizoites grow through several shell changes by hermit crabs, and a number of forms are capable of surviving the final deposition of the shells.     

各种类型河蟹育苗用水的水质分析

近几年,河蟹人工育苗已成为我省沿海种苗培育单位的重要产业 ,随着育苗规模的不断扩大及所带来的可观经济效益,各地又因地制宜发展起地下海水、浓缩海水的育苗生产,为搞清这几种育苗水体的水质特点 ,作者对这几种水体进行了分析检测,以服务于生产 ,为河蟹育苗的健康发展提供科学依据。１工作内容和方法１．１采样点自然海水采于营口市老边区三道沟和盘锦市二界沟;浓缩海水采于营口市青石岭育苗室及营口盐 　种型苗水ｐ ＣＤ营盐含量Ｔａｂ .1　ｐＨ ,ＣＯＤａｎｄｎｕｔｒｉｔｉｏｎｓａｌｔｏｆｅｖｅｒｙｋｉｎｄｏｆｂｒｅｅｄｉｎｇｗａ…     

Spatial and Temporal Variability in a Vertical Section Across the Alaskan Stream and Subarctic Current

In the central North Pacific Subarctic Gyre, CTD hydrographic measurements were carried out yearly in late June from 1990 to 1998 at 9 stations along 180° meridian from 48°N to 51.2°N. Vertical sections of 9-year means, anomalies for each year and others of potential temperature, salinity, potential density and geostrophic velocity (referred to 3000 m) were calculated based on this data set. Empirical Orthogonal Function (EOF) analysis was adopted in the investigation of spatial characteristics and its temporal variation in vertical sections. The spatial distribution of the 1st mode EOF of velocity shows the westward Alaskan Stream and the eastward Subarctic Current. This mode explains 37.6% of the total variance. Two positive maxims appear in its amplitude in 1991 and 1997, which is similar to the variation in volume transport of the eastward Subarctic Current. These variations are closely related to the vertical movement of Ridge Domain deep water.     

Long-term biological effects of petroleum residues on fiddler crabs in salt marshes

In September 1969, the Florida barge spilled 700,000L of No. 2 fuel oil into the salt marsh sediments of Wild Harbor (Buzzards Bay, MA). Today the aboveground environment appears unaffected, but a substantial amount of moderately degraded petroleum still remains 8-20cm below the surface. The salt marsh fiddler crabs, Uca pugnax, burrow into the sediments at depths of 5-25cm, and are chronically exposed to the spilled oil. Behavioral studies conducted with U. pugnax from Wild Harbor and a control site, Great Sippewissett marsh, found that crabs exposed to the oil avoided burrowing into oiled layers, suffered delayed escape responses, lowered feeding rates, and achieved lower densities. The oil residues are therefore biologically active and affect U. pugnax populations. Our results add new knowledge about long-term consequences of spilled oil, a dimension that should be included when assessing oil-impacted areas and developing management plans designed to restore, rehabilitate, or replace impacted areas.     

Autotomy in porcelain crabs is an effective escape mechanism from rockfish predation

Porcelain crabs possess a ‘hair‐trigger’ propensity to autotomize their chelipeds (claws), and laboratory studies have demonstrated that this ability is highly effective in avoiding predation from other crabs. However, porcelain crabs are also subject to predation from fishes, which use a very different means of capture. In this study, we investigated whether autotomy in porcelain crabs is also effective against predation by fishes. To do this, we examined stomach‐contents data from four common species of kelp‐forest rockfishes and determined the frequency of disassociated chelipeds (those with no associated bodies) in porcelain crabs and in brachyuran crabs, which do not readily autotomize their chelipeds. We found that disassociated chelipeds of porcelain crabs were six times as common as those of brachyuran crabs (35% of the remains of all porcelain crabs versus 6% of the remains of all brachyuran crabs). We interpret this difference to be evidence that, through autotomy, porcelain crabs escaped ingestion of their entire bodies, and thus certain mortality, at a higher rate than did brachyuran crabs. We conclude that autotomy constituted an effective escape strategy from rockfish predation. This evidence, in conjunction with previous studies, suggests that autotomy of chelipeds in porcelain crabs is an effective anti‐predatory strategy against phylogenetically disparate predatory groups.     

Observations of the Alaskan Stream near Samalga Pass and its connection to the Bering Sea: 2001–2004

Year-long moorings were deployed across the Alaskan Stream near Samalga Pass (169°W) on two occasions, first in 2001–2002 (5 moorings) and again in 2003–2004 (3 moorings). Currents were measured throughout the water column, and temperature and salinity were measured at selected depths. Satellite altimetry and satellite-tracked drifters revealed a well defined Alaskan Stream, with the largest near-surface average speeds (>60 cm s⁻¹) and highest eddy kinetic energy just upstream from the mooring sites. Excluding periods when large eddies disrupted the flow, transport in the Alaskan Stream ranged from 10 to 30×10⁶ m³ s⁻¹. The estimated mean transport in 2001–2002 was 19×10⁶ m³ s⁻¹, and in 2003–2004 was 21×10⁶ m³ s⁻¹. Large (diameter>200 km), anti-cyclonic eddies were not uncommon in the vicinity of Samalga Pass (14 times in 20 year period, 1992–2012). Although there were no such eddies observed during the period 2000–2003, one of the largest ever recorded eddies occurred in spring 2004. In addition, smaller eddies occurred on several occasions. Eddies disrupted the flow, shifting the Alaskan Stream farther off shore and were clearly evident in both the satellite imagery and the mooring data. Other energetic events, which were less evident in the satellite records, but clearly evident in the mooring measurements, also disrupted the flow. In addition to the moorings in the Alaskan Stream, pressure gauges were placed in Samalga Pass and a single mooring measuring currents was placed in the Aleutian North Slope Current (ANSC) in the Bering Sea. The alongshore, near-surface flow measured at the moorings deployed on the 1000-m isobaths in the Alaskan Stream and the ANSC were significantly correlated with the bottom pressure time series. In addition, at periods longer than 14 days, the bottom pressure measured at the mooring sites in Samalga Pass was significantly correlated with the sea surface height measured by the satellites. The eddy kinetic energies measured from the satellites and from moorings were also significantly correlated.     

舟山群岛东侧海域蟹类群落结构及其与环境因子的关系

根据2018年4月(春季)和10月(秋季)在舟山群岛东侧海域(29°10′25.54"～30°45′00"N,122°53′3.88"～124°48′28.31"E)开展的渔业资源底拖网调查所获得的蟹类数据,研究了该海域蟹类资源的种类组成、优势种、生物多样性等群落结构特征,同时分析了蟹类数量分布及其群落结构与温、盐等环...     

The geology,geochemistry and Ni-Cu-PGE potential of mafic-ultramafic bodies associated with the Dido Batholith,North Queensland,Australia

Four elongate, km-scale, mafic to ultramafic bodies (UMB) were identified within the Ordovician-Silurian Dido Batholith, north Queensland, and were assessed for Ni-Cu-PGE fertility. The UMB comprise layered cumulate sequences and represent open-system intrusions emplaced at mid-crustal levels. The UMB are divided into two petrographically and geochemically distinct types: (1) low-Fe UMB (3 intrusions), comprising dunites, wehrlites, troctolites and olivine gabbro which contain variable amounts of olivine (Fo_85–72), clinopyroxene (Mg# 0.87–0.73), plagioclase (An_92–72) and chromites; and (2) high-Fe UMB (1 intrusion), comprising dunites, wehrlites and pyroxenites which lack chromites, contain abundant early crystallising Fe-Ti oxides and hornblende, and less primitive olivines (Fo_78–72) and pyroxenes (Mg# 0.87–0.73). The calculated parent magmas of the low-Fe UMB contained 8–10 wt% of both MgO and FeO_t, whereas the high-Fe UMB parent magmas were more evolved, having higher FeO_t (12–16 wt%) and lower MgO (6.2–8.2 wt%), Ni and Cr concentrations. The parent magmas of the Dido UMB are interpreted as mantle-derived arc rift or backarc tholeiites, and mineral compositions suggest the UMB are similar to arc-cumulate, Klamath-type intrusions. Crustal contamination during ascent is suggested to be responsible for the LREE-enriched and Nb- and Ti-depleted nature of the UMB parent magmas. A two-component Sr-Nd isotope mixing model suggests that the addition of variable amounts (<5% in the low-Fe UMB and 9–10% in the high-Fe UMB) of 2000–2500 Ma igneous crustal contaminant to tholeiitic melts derived from a slightly enriched mantle source can account for isotopic compositions of the UMB. Although the mantle-derived, crustally contaminated nature of the parent magmas are positive factors for magmatic sulphide mineralisation, economic mineralisation has not been found associated with the UMB. Geochemical discriminators, such as Cu/Pd and Ni-depletion, suggest that the magmas that formed the km-scale UMB were chalcophile element-depleted, having undergone a previous S-saturation event (i.e., significant sulphide-deposition) at depth. The slight PGE-enrichment in the high-Fe cumulates (up to 160 ppb of both Pt and Pd) is suggested to be due to the addition of small amounts of PGE to the high-Fe magmas from an external source. There is no evidence to suggest that large volumes of PGE-enriched sulphides were added to the UMB magmas. These findings, in addition to the knowledge that most large deposits are associated with intracontinental settings rather than convergent settings, determined that the investigated Dido UMB are low-priority Ni-Cu-PGE targets. However, the likelihood that the Dido UMB were emplaced in local extensional regimes within subduction-related environments, i.e., a similar geodynamic setting to economic deposits such as Aguablanca (Spain), requires that other UMB in the Dido area are assessed on an individual basis.