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Corals were exposed to drilling mud for 24 hr and then allowed to recover for 48 hr in clean seawater. Depending on the concentration and the mud used, exposure produced either an increase or decrease in free amino acid (FAA) pool size. Aspartate was affected to a greater degree than other amino acids. No clear instance of recovery could be ascertained after 48 hr in clean seawater. In several cases, corals, apparently unaffected by a 24 hr exposure, nevertheless suffered significant changes in the FAA pool during the 48 hr recovery period. Thus, the degree of toxicity of the drilling mud could not be accurately predicted from the 24 hr exposure data. In many cases, the choice of a normalizing parameter determined whether two sets of data were significantly different or not. Accurate effects assessment depends on a comparison of several methods of normalization to confirm statistical results.

Perkinsus marinus, a protozoan parasite of oysters, is an important cause of oyster mortality in the Gulf of Mexico and along the south-eastern coast of the United States (Hofstetter, 1977; Quick & Mackin, 1971). Infections are patchily distributed on many reefs, often with uninfected oysters adjacent to infected oysters. The primary mechanism of transmission from one oyster to another is through the water (Ray, 1954; Mackin, 1962; Andrews, 1965). Because dilution rapidly reduces the number of infective elements below the dosage required to initiate new infections (Andrews, 1979), transmission is most efficient over very short distances and declines rapidly within a few metres of the source.

A sulfurous brine seep at the East Flower Garden Bank, northwest Gulf of Mexico, produces conditions conducive to the growth of a luxuriant prokaryotic biota. Hydrodynamic cropping continually harvests this biota and distributes it to sandy-bottom and hard-bank benthic communities downstream of the seep. Consequently, both macro- and meiofaunal abundances are dramatically increased above the regional norm in parts of the seep system. When sulfide is present, the lower Bilaterian groups belonging to the meiofauna dominate the community; without sulfide, macrofaunal groups, particularly crustaceans, dominate the community. Outside the influence of the seep, meiofaunal copepods predominate. Changes in taxonomic composition and abundance indicate that the sandy-bottom benthos at 70–80 m depth at the East Flower Garden bank is foodlimited and that, under these conditions, meiofauna, particularly the higher Bilaterian groups, dominate the community numerically. Perhaps, under food-limiting conditions, meiofauna compete favorably with macrofauna for food.

1. 1. Three turbellarians, Kuma sp., Solenofilomorpha c.f. funilis and Parahaploposthia thiophilus, were exposed to oxia, anoxia, sulfide and cyanide and the resulting changes in CO2 production from glucose monitored. 2. 2. All three species were capable of aerobic metabolism. 3. 3. CO2 production in the oxybiont Kuma, decreased under anoxia, sulfide exposure and cyanide exposure. 4. 4. CO2 production in the two thiobiotic species decreased under anoxia, but aerobic metabolism was cyanide and sulfide insensitive. CO2 production under oxia was much higher in Solenofilomorpha than Parahaploposthia, however. 5. 5. Hence, thiobiotic species are sulfide-insensitive organisms capable of aerobic metabolism, but aerobic capability differs markedly among taxa.

Calcification rate in the coral Acropora cervicornis was reduced significantly when exposed for 24 h to 100-ppm kaolin, but was unchanged in corals exposed to 50-ppm kaolin. Calcification rate returned to control levels during a 48-h recovery period. Most free amino acids (FAA) in the FAA pool decreased significantly in corals exposed to 100-ppm kaolin, but were unchanged in corals exposed to 50-ppm kaolin. After a 48-h recovery period, the FAA pool remained considerably below control levels in the 100-ppm exposed corals and dropped below control levels in the 50-ppm exposed corals. Calcification rate dropped less and later during the exposure period in the growing tip than in sections further down the stalk. The reduction in FAA pool size was considerably larger in the growing tip than further down the stalk. Soluble protein concentration remained unchanged during both exposure and recovery. The data are consistent with the interpretation that turbidity not only causes a decrease in photosynthetic rate and the synthesis of small molecules, but also causes a large increase in the utilization of stored organic molecules for such metabolically costly processes as mucus production and sediment removal.

The burrowing behavior of the holothurian Leptosynapta tenuis, its lebensspuren, and the types of peristaltic waves used in movement and burrow irrigation are described. Particle size selection is a function of accessability of grains. L. tenuis cannot distinguish between particle sizes but nevertheless ingests small particles in a lesser proportion than that found in the surrounding sediment. Feeding rates are 2900–5500 g · yr−1 · animal−1. These rates are strongly dependent on temperature. Computation of a sediment mixing budget shows that of all the sediment ingested, 51% is ingested from the top 1/2 cm of sediment, 75% from the top 3 cm. The significance of the funnel as a ‘tool’ to exploit the top 1/2 cm of sediment is discussed. L. tenuis differs from other deposit feeders in that (1) it removes small particles from the surface sediment during its reworking activities, (2) it reworks sediment downward as well as upward, (3) its reworking activities tend to increase the stability of the upper 3 cm of the sediment, and (4) because so much sediment is ingested from the top 1/2 cm, it reworks an entire sediment column less efficiently per gram of sediment ingested than many other deposit feeders.

The death assemblage is an important source of information about temporal variability in community composition. The living community and the short-term death assemblage have been studied at a sandy-bottom station in the Laguna Madre, Texas. Abundance peaks of living species are usually followed by long-term abundance increases of the same species in the death assemblage. This phenomenon provides a tool for investigating between-sampling-occasion events in the preservable component of the living community. Given a six-week sampling regimen, approximately 90% of all individuals settle, live and die during the period between consecutive sampling occasions and are not collected alive. Thus, larval settlements are consistently underestimated by about 90% from data on the living community. Comparisons of year-to-year variability in settlement and survivorship of settled individuals in the youngest age classes may be considerably in error. Better estimations of actual settlement and survivorship can be made from the death assemblage provided that the rate of taphonomic loss can be quantified. The rate of taphonomic loss can be expressed as the species' half-life, the time required for the destruction of 50% of the individuals that were added to the death assemblage following settlement. Half-lives for the smallest size classes in the death assemblage at this site are about 100 days.

The post-mortem fate of shells added by natural mortality to modern death assemblages was studied to determine the importance of taphonomic loss during the initial stages of the formation of a fossil assemblage. Individuals are added to the living community in pulses, usually by larval settlement. These input pulses usually are followed by discrete input pulses into the death assemblage. The decay of these discrete input pulses in the death assemblage can be used to measure the rate of taphonomic loss as expressed by the half-life of a pulse. For instance, if a species has a half-life of 125 days and the input pulse begins with 500 individuals, then the number of shells remaining after one half-life (125 days) is 250 shells. At two sites on the Texas coast, the longest half-lives did not exceed one year for any of the 13 species which produced input pulses during the study period. Little net addition to the death assemblage could be detected in spite of the transitory addition of hundreds of shells as input pulses. These rapid decay rates show that death assemblages do not accumulate at the rate at which organisms die. Some species, such as the infaunal bivalve Tagelus plebeius , did not decay measurably. We predict that decay rates drop substantially with depth in the sediment so that individuals which die at depth or are rapidly reworked below the sediment surface have a greater chance of preservation. The final composition of death assemblages is probably little related to the actual numerical input from the potentially preservable component of the living community.

Boonea (= Odostomia) impressa is a common ectoparasite of oysters. In the laboratory, small oysters (Crassostrea virginica) parasitized by natural densities of B. impressa produced 75 % less new shell than unparasitized oysters. Shell deposition rates of previously parasitized oysters increased significantly after all B. impressa were removed. Thus, the decrease in growth rate, although significant, apparently was not permanent. B. impressa preferentially parasitized small, living oysters (≤2.5cm) in the field, even though a higher percentage of large, living oysters (>2.5cm) was available. The snails maintained an aggregated distribution on the oyster reef. The number of B. impressa per oyster clump was positively correlated with the number of living oysters per clump, however some clumps with few or no living oysters had many B. impressa. Thus, food availability only partially explained the pattern of distribution. B. impressa was very mobile. About 50 % of the population moved in one week. Reproduction occurred throughout the year with a peak period in May. Recruitment was greatest in July, however new recruits were observed throughout the year. The reduction in growth rate of parasitized oysters, the snaiľs propensity towards parasitizing small oysters and the snail's tendency to be contagiously distributed suggests that B. impressa potentially exerts a significant influence on the population structure and health of oyster populations.

1. 1. The response of the free amino acid pools of two nereid polychaetes, Neanthes succinea and Laeonereis culveri to both increased and decreased salinities was examined. In both species, glycine and alanine accounted for most of the observed change in the total free amino acid (FAA) pool size. 2. 2. Glutamine values increased under hypo-osmotic conditions suggesting that this amino acid plays a role in nitrogen storage during the reduction in FAAs which occurs with reduced salinity. 3. 3. The salinity response was superimposed on a “laboratory stress” response characterized by a generalized increase in the FAA pool size. The two responses appeared to be additive in nature. 4. 4. Significant differences in the responses of individual amino acids between these two species indicates that interspecific variation exists in the response to salinity change in nereid polychaetes.

The effect of used drilling muds on coral health was examined by monitoring changes in calcification rate and soluble tissue protein concentration in the coral Acropora cervicornis. Exposure to 25 ppm (v/v) of one mud for 24 h reduced calcification rate in the growing tips by as much as 62%. In recovery experiments, corals were exposed to drilling muds for 24 h; some of them were allowed to recover in clean seawater for 48 h. After the 24-hour exposure, calcification rates were significantly less than those of the controls. After a 48-hour recovery period, calcification rates returned to control levels for one mud but were still significantly below control levels for another. The results indicate that the capacity for recovery after exposure cannot be predicted from the results of experiments on exposure only. Recovery capacity must be independently verified for all studies on the effects of short-term exposure to drilling muds.

Rates of shell production rarely exceed 500 g CaCO3.m-2yr-1 in clastic sediments. Loss of shell carbonate by dissolution greatly exceeds loss by bioerosion and abrasion in most habitats. Rates of shell dissolution in modern sediments, estimated from rates of organic carbon degradation or measured directly, usually exceed 1000 g CaCo3.M-2yr-1. This taphonomic loss is concentrated at or just below the sediment-water interface in the taphonomically-active zone (TAZ). Consequently, except where rates of shell production are very high or rates of organic carbon degradation very low, shells cannot permanently accumulate on the sea floor. Preservation requires rapid burial, usually by physical ‘event’ processes, to slow down taphonomic loss. Only near the base of the TAZ does the long-term sedimentation rate become an effective mediator of shell preservation as sediment accumulation gradually removes buried shell material from the taphonomically-active zone.

During most offshore drilling operations, drilling muds are routinely discharged into surrounding waters. Because corals are relatively sensitive to many environmental perturbations and can be adversely affected by offshore drilling operations, the effects of drilling muds on corals have received considerable attention. Because drilling muds are discharged intermittently, only periodic exposures of short duration should impact nearby coral reefs. To fully assess the impact of a drilling mud discharge on corals requires an assessment of the capacity for corals to recover from short-term exposure. The purpose of this study was to assess the relative toxicity of a number of muds that were slated for marine disposal for the coral Acropora cervicornis after a 48-hr recovery period. Calcification rate and free amino acid pool were investigated.

The digestive tract functions in the storage, metabolism, and excretion of heavy metals in invertebrates. The importance of the digestive tract and the processes governing digestion and absorption of nutrients in heavy metal uptake is becoming increasingly clear. The results of this study suggest that in order to understand the processes controlling heavy metal uptake in invertebrates, it will be necessary to investigate the role that digestion and absorption play in determining the transport rate of metals across the gut wall into the blood. For example, some amino acids increase metal absorption rates, whereas other compounds, such as phytate, decrease metal absorption rates. The results also suggest that experimental designs to investigate metal absorption must include an appreciation of the significant role that the feeding state of the animal (e.g. fed or starved) and the role chelators, particularly those produced by the organisms themselves during digestion, may play in the observed uptake rates of metal ions.

A review of the maximum longevity of bivalves and gastropods indicates that a greater than average number of life spans coincide with the periods of long-term cycles in marine communities. Apparently, long-term cycles exert an important influence on marine communities by affecting the life spans of constituent species. Gastropods and bivalves are affected differently, longevities being determined by some cycles more than others in each group. Overall, molluscan longevities tend to be slightly longer than the corresponding cycle suggesting that there is selection pressure for life spans slightly longer than the cycle controlling recruitment success and generational replacement.

Publisher Summary This chapter describes anoxic sulfide-rich brine of nearly ambient temperature, which percolates from the sea floor, forming a small, shallow lake of dense water in a depression at the eastern margin of the East Flower Garden (EFG) bank. Residence time for the brine in the lake is less than one day. Brine overflows the lake and is substantially mixed with seawater in the axis of a 60 m long canyon extending from the lake to the bank edge, where dilutions are greater. The chemical composition of the brine indicates that it is a product of dissolution of the salt by seawater percolating through cracks, faults or permeable strata. Sulfide-oxidizing bacteria are abundant at the brine seawater interface and on the canyon floor where mixing brine and entrained seawater flow in a recognizable stream along the bottom. The EFG seep provides an example of a possible management technique for brine discharges.

Prevalence (percent of oysters infected) ofPerkinsus marinus and infection intensity were measured in oysters from 49 sites in the Gulf of Mexico. Prevalence was less than 50% at only one site. Both prevalence and infection intensity were correlated with condition index, salinity, and a measure of local agricultural activity. The regional distribution ofP. marinus was patchy on spatial scales of 300 km or less and 1,500 km or more. Three regional foci of infection could be distinguished: the north central coast of Texas, central Louisiana west of the Mississippi River, and the southwestern coast of Florida. Lowest infection levels were recorded along the north central and northeastern Gulf, particularly east of the Mississippi River. The spatial distribution of infection varied with the salinity regime; however, other factors also explained part of the regional patterns observed. These included factors associated with man’s activities such as agricultural and industrial activity and the average annual temperature regime.

The death assemblages in upper Copano Bay and upper Laguna Madre, Texas, were compared with the living communities as sampled over a two-year period in order to determine how taphonomy and time-averaging affect paleocommunity reconstruction. The living and death assemblages were compared using taxonomic composition, numerical abundance, diversity, biomass, and trophic and habitat proportions. Taxonomic composition, particularly adult taxonomic composition, and the biomass of the death assemblage more accurately reflect the characteristics of the living community than do numerical abundance and other community attributes based upon numerical abundance such as diversity. Taxonomic composition and biomass are less modified by taphonomy and time-averaging, because they are temporally more persistent characteristics of the community. Community and paleocommunity attributes are not equivalent, because the paleocommunity is described using time-averaged data. Ecological theory must be supplanted by paleoecological theory that takes into account this temporal component.

In 1985, the Geochemical and Environmental Research Group (GERG) at Texas A&M University (College Station, Tex.) reported in Eos [Brooks et al, 1985] the discovery of chemosynthetic organisms (bivalves and tube worms) at two sites on the Gulf of Mexico continental slope. The presence of gas hydrates at five sites, some associated with oil-stained sediments, was also detailed. In the subsequent year, follow-up cruises and submersible dives (using the Johnson Sea-Link, owned and operated by the Harbor Branch Foundation, Fort Pierce, Fla., and the Navy NR-1) investigated the physiology, biochemistry, and distribution of these chemosynthetic organisms.

The concentration of free amino acids (FAA) increases in three species of bivalves, Tagelus plebeius, Rangia cuneata, and Phacoides pectinatus, taken from ever increasing depth in the upper 72 cm of a core from a mesohaline, sandy-bottom site in Copano Bay, Texas. Analysis of museum shells of known age indicates that [FAA]* increases with shell age (time-since-death) as the proteinaceous matrix gradually breaks down. Estimation of relative age (one shell older than another) in shells less than a few hundred years old is readily accomplished using a measure of [FAA]. The estimation of absolute age (actual time-since-death) depends on an independent calibration. Museum shells of known age offer one possible method. The glycinelalanine ratio decreases with time either because the rate of alanine production increases or because glycine diffuses out of shells more rapidly. Hence [glycine] is a useful estimator of age for relatively young shells and [alanine] or [glutamic acid] for older shells. Age estimates from calibration curves using museum specimens of T. plebeius and R. cuneata and independent estimates based on sediment accumulation rates agree for shells taken from the Copano Bay site. Measuring [FAA] provides a method to appraise the degree of time averaging in modern death assemblages because the relationship of shell age and burial depth can be determined. [FAA] changed little in shells below 72 cm in the core indicating that an increase in time averaging may have occurred below that depth, whereas, in the upper 72 cm, changes in death assemblage