Although many researchers have examined the phenomenon of intertidal zonation and its structuring processes in rocky habitats, similar studies concerning soft-bottom habitats are relatively uncommon. The bivalve assemblage of Polymesoda caroliniana (Corbiculidae) and Rangia cuneata (Mactridae), common in the shallow subtidal and intertidal zones of the mesohaline-oligohaline regions of southeastern United States estuaries, allows some analogies to previously studied rocky intertidal communities in that the adults of these bivalves are large (20-70 mm in shell length), and move very little, making the populations relatively easy to census and manipulate. I conducted field surveys and manipulative experiments on populations of R. cuneata and P. caroliniana between 1982 and 1984 in the Ochlockonee-Sopchoppy estuary of northwestern Florida. The emphasis of the research was description of the vertical distribution of members of each species, and analysis of factors controlling these distributions, including recruitment, physiological factors, disturbance, and potential competitive effects. Results indicate that R. cuneata is a subtidal inhabitant whose upper bound is controlled by physical factors, including physiological tolerances to such factors, and probably a lack of sufficient time for feeding and respiration. Recruitment of R. cuneata is highly variable, and results in populations dominated by single age classes. P. caroliniana is shown to be an intertidal inhabitant. The lower bound of the P. caroliniana population is determined, in an ecological sense, by larval settlement, but in an evolutionary time frame is probably controlled by biological factors such as predation and disturbance by predators and bioturbators. P. caroliniana seems to recruit regularly, but juvenile mortality is high, so recruitment to the adult population is low. No competitive effects between adult P. caroliniana and R. cuneata were found. / Source: Dissertation Abstracts International, Volume: 49-03, Section: B, page: 0601. / Major Professor: William Heard. / Thesis (Ph.D.)--The Florida State University, 1987.

acase@tulane.edu

The fauna and flora living on the bay scallop, Argopecten irradians, was examined from twenty-five consecutive monthly collections. The nematode fauna of scallops differed from that of nearby sediments and seagrasses in that it was less diverse and was dominated by three species, Viscosia macramphida, Syringolaimus striatocaudatus, and Chromadora nudicapitata. These species were rare in sediment samples and common, though not as abundant, on seagrasses. They accounted for 79.3% of the total individuals on scallops. The simplicity of this nematode assemblage was exploited in field and laboratory experiments designed to uncover the ecological factors responsible for the temporal variation of the dominant species. / Initial field experiments justified the view of scallop shells as isolated communities because the swimming activities of scallops did not remove the shell's nematode fauna, and space experimentally made available on a scallop shell was not appreciably recolonized over a four-hour period. Consequently, the system could be studied experimentally. / The major finding of the research was discovering that each species responded to a different ecological factor. Viscosia was most abundant on scallop shells in late summer. Its abundance coincided with a peak in diatom abundance, its preferred food. Chromadora was abundant in the spring on young scallops that had recently detached from blades of the seagrass Thalassia testudinum. At that time, Chromadora was the most abundant nematode on the blades, so its abundance on newly steeled scallops was a reflection of the recent history of the shell. It remained abundant on scallops until the early summer. A long-term field recolonization experiment determined that immigration of Chromadora from seagrasses was not responsible for the continued success of the shell populations. Syringolaimus increased in abundance over the course of the study, and was the overall dominant on scallop shells once Chromadora populations declined. A laboratory culture experiment determined that Syringolaimus was not able to competitively exclude Chromadora under conditions approximating those in the field. Rather, the species coexisted in densities consistent with their field values. / Source: Dissertation Abstracts International, Volume: 47-02, Section: B, page: 0465. / Thesis (Ph.D.)--The Florida State University, 1985.

A need exists for information on sedimentary microbes, expecially at the level of specific populations, and particularly with respect to their interactions with benthic macrofauna. Two examples were documented. / First, biochemical and conventional analyses were used to characterize the microbial food resources and digestive efficiency of Ptychodera bahamensis, an enteropneust hemichordate. Sediment was collected from freshly extruded fecal casts and adjacent feeding depressions. There were no significant differences between casts and depressions in granulometry, density of meiofauna, and concentrations of photopigments. Nematodes in casts were larger than those in depressions. Total phospholipid, ester-linked fatty acids (PLFA) were 30% lower and phospholipid phosphate was 49% lower in casts. Concentrations of 33 fatty acids were lower in casts, indicating that the hemichordate digests a wide variety of microorganisms. Only 18:1$\omega$7c, characteristic of Gram-negative organisms, was not lower in casts than in depressions. P. bahamensis either cannot digest this functional group of bacteria or contributes gut microbes containing 18:1$\omega$7c to sediment passing through its alimentary canal. / Second, the same methods were used to characterize the microbial populations within the burrow of Callianassa trilobata, a decapod crustacean. Sediment was collected from the burrow lining, burrow matrix, and ambient, subsurface sediment. The lining and matrix were composed of fine-grained material compared to sandy, ambient sediment. Meiofauna were most abundant in ambient sediment, not in the burrow as has been found for other species of macrofauna. Lipid analyses indicated that relative to the matrix and ambient sediment, the lining abounds with pro- and eukaryotic biomass. PLFA were assigned to functional groups of microorganisms to assess spatial variations in the absolute abundance and relative proportions of microbial populations. Dominance of prokaryotes was pronounced in all three areas, especially the matrix. The lining was the most aerobic location, but anaerobic microhabitats simultaneously harbored sulfate-reducing bacteria. The ratio of Gram-positive to Gram-negative bacteria increased from lining to matrix to ambient sediment. The Trans/cis ratio of 16:1$\omega$7 indicated that prokaryotes in the matrix were starved. / Source: Dissertation Abstracts International, Volume: 49-03, Section: B, page: 0601. / Major Professor: Paul A. LaRock. / Thesis (Ph.D.)--The Florida State University, 1987.

Sediment cores in the North Atlantic show evidence of periodic large-scale ice discharge events between 60 kyr and 10 kyr before present. These so-called Heinrich Events (HEs) occurred with a typical period between 5 kyr and 10 kyr. During each HE, a significant amount of ice was discharged from the Laurentide ice sheet into the North Atlantic. This input of freshwater through the melting of icebergs is thought to have strongly reduced the strength of the Atlantic thermohaline circulation. / One theory for HEs is that they are due to an internal oscillation of the ice sheet under constant forcing. This implies that past multi-millennial scale climate variations in the North Atlantic region may have been driven by variations in the Laurentide ice sheet and were not externally forced by climate change or sea level variations. A second theory for HEs requires some variable external forcing on an unstable ice sheet to produce a discharge event. / Using the 3-D ice sheet model of Marshall and Clarke (1997a,b), which includes ice sheet dynamics and thermodynamics, the possibility of internal oscillations within an ice sheet is verified and an analysis of the mechanisms associated with these oscillations is performed. The bed topography and strain heating are found to be critical for the formation and development of fast moving ice streams, which lead to large iceberg calving. In addition, the calving parameterization is found to be an important factor in the ability of the model to periodically discharge large amounts of ice.

<p> Knowledge of species distribution and habitat associations are essential for conservation measures. Such information is lacking for many marine species due to their occupancy of broad and ephemeral habitats that are difficult to access for study. Sea turtles, specifically the surface&minus;pelagic juvenile stage of some species, are a group for which significant knowledge gaps remain surrounding their distribution and habitat use. Recent research has confirmed the long&minus;standing hypothesis that the surface&minus;pelagic juvenile stage occurs within surface&minus;pelagic drift communities (SPDC). Within the North Atlantic and surrounding basins, the holopelagic macroalgae <i> Sargassum</i> spp. dominates SPDC and serves as a remotely&minus;detectable indicator of SPDC. The present study focuses on surface&minus;pelagic habitats of four sea turtle species and addresses knowledge gaps using two approaches: habitat mapping and behavioral examination. Remote sensing techniques were used to identify SPDC, and satellite telemetry to examine behavior. This work was conducted in three parts and is presented in three chapters. </p><p> Imagery collected from the Landsat satellites (5 and 7) was used to quantify the area of SPDC (km²). Approximately 1,800 Landsat images collected from 2003&ndash;2011 were examined for SPDC. The first chapter discusses the abundance, seasonality, and distribution of SPDC within the eastern Gulf of Mexico waters where surface&minus;pelagic green, hawksbill, Kemp&rsquo;s ridley, and loggerhead turtles are known to occur. SPDC was found year&minus;round within the eastern Gulf of Mexico, and the amount of habitat peaked during summer months. The amount of SPDC within the eastern Gulf of Mexico varied annually with peaks in 2005, 2009, and 2011. High concentrations of SPDC were discovered within offshore waters of the northeastern Gulf of Mexico and southern West Florida Shelf. </p><p> Within the second chapter, the behavior of 10 surface&minus;pelagic juvenile Kemp&rsquo;s ridleys was examined using satellite telemetry. Using remotely&minus;sensed imagery, the sea surface habitats used by tracked turtles were examined. Surface&minus;pelagic juveniles are hypothesized to be principally passive drifters. The behavior of tracked turtles was examined to determine if they exhibited periods of active and passive behavior, which may indicate periods of swim and drift. The proximity of tracked turtles to remotely&minus;detected SPDC was examined when coincident Landsat imagery was available (within one day of the turtle&rsquo;s position). Turtles were tracked for 36.5 days (mean) and exhibited primarily passive behavior during the tracking period. The satellite transmitters messaged frequently and reported temperatures significantly higher than sea surface temperatures. Landsat imagery was available coincident to the tracks of nine individuals. SPDC was present within 74% of images, and the mean distance between tracked turtles and SPDC was 54 km. Close associations between tracked turtles and SPDC were documented for four individuals. Results suggest that the tracked turtles spent a majority of the time drifting within SPDC. </p><p> The final chapter discusses the density of SPDC within northern and western Gulf of Mexico waters from 2009&ndash;2011. Seasonal abundance peaks occurred throughout the study area, but the timing varied. SPDC peaked earlier (late spring) within the northwestern Gulf of Mexico. Moving eastward, the timing of seasonal peaks shifted progressively later during the year. Within the western portions of the study area, SPDC was found to be significantly higher than in the eastern Gulf of Mexico. </p><p> The eastern Gulf of Mexico may provide critical developmental habitats for several North Atlantic sea turtle species. Additional study is necessary to determine if portions of the western Gulf of Mexico could serve in a similar capacity. SPDC is extremely vulnerable to anthropogenic impacts, specifically oil spills and the occurrence of persistent marine debris. Conservation of SPDC may be challenged by its ephemeral nature; however, the results presented herein could advise conservation efforts (e.g., delineation of critical habitat). The present study described spatial patterns of SPDC occurrence, regions of high abundance, and seasonality. The description of the behavior surface&minus;pelagic sea turtles offers refinements to the spatial distribution of this life stage. These results, coupled with information on circulation patterns and the distribution of sea turtle nesting beaches, can be used to better predict when and where sea turtles and SPDC may be found. For example, the year&minus;round persistence of SPDC within the eastern Gulf of Mexico and the location of major nesting beaches located upstream support the area&rsquo;s designation as critical habitat for surface&minus;pelagic green, hawksbill, Kemp&rsquo;s ridley, and loggerhead turtles.</p>

Thesis (Ph.D.)--North Carolina State University, 2006. / (UnM)AAI3223189. Adviser: David B. Eggleston. Source: Dissertation Abstracts International, Volume: 67-06, Section: B, page: 2996.

No description available.

A study was done on a rocky intertidal community in Puerto Penasco, Sonora, Mexico in the summers of 1997--1999 in order to determine if the ENSO of 1997--1998 had an effect on population densities of selected macroinvertebrates. Two replicate transects were laid perpendicular to the sea edge and a census of 21 macroinvertebrate species was taken in the summers of 1997, 1998 and 1999. A significant decrease of species densities occurred in 1998 when the mean sea surface temperature (SST) was more than 2°C warmer than in 1997 due to the 1997--1998 ENSO event. A phenomenon was also observed in 1998 where some species changed, compared to 1997, their vertical distribution in the intertidal from shallow to deeper waters, with a subsequent return to a more expected distribution in 1999. Also a comparison of 1997 and 1976 densities showed an increase in 1997 in abundances of those species with southern geographic ranges and a decrease of those with northern geographic ranges. This was correlated with an increase of mean SST of 1.9°C between the 1970's and the 1990's.

The ecology and behavior of nine species of anemonefishes and ten species of sea anemones were studied at a variety of sites in the region of Madang, Papua New Guinea. More than 95% of the suitable anemones in the region were occupied by anemonefishes. Each species of fish had a distinct pattern of host specificity and population surveys at three replicate reef sites within four locations situated at varying distances from the mainland (nearshore, mid-lagoon, outer barrier, and offshore), indicated that each species of host anemone and anemonefish lived within a particular range of locations. Recruitment was monitored to anemones in natural populations and to anemones that had their resident fishes removed. Significantly more fish recruited to anemones without residents. Each fish species recruited into the host species and locations occupied by their adults. Thus, recruitment had a strong effect on patterns of anemonefish host specificity and distribution, but fish abundance was limited by the availability of anemones. / The host location and association behaviors of laboratory raised anemonefishes were examined. Juvenile anemonefishes that were competent to settle were released in the field at different distances and orientations away from anemones. The fishes were only attracted toward particular species of anemones, and they used chemical cues released from anemones and rheotaxis to locate their hosts. Resident fishes were aggressive toward new recruits and usually prevented them from staying with anemones. Recruiting anemonefishes contacted the tentacles of most anemone species without harm, but in some cases the fishes were stung. Forced contact tests with anemonefish eggs, larvae, juveniles, and adults showed that the fish species tested developed some level of protection from anemones during metamorphosis from a pelagic larva to a benthic juvenile. Forced contact tests with fishes reared in complete isolation from anemones demonstrated that the protection was innate for some species of anemonefishes. However, juvenile fishes still went through acclimation behavior during the initial interaction with an anemone, even if the fishes were innately protected. Immunological studies with polyclonal antibodies to anemone mucus antigens showed that anemonefishes acquire anemone antigens in their mucus coat during their association with anemones. / Source: Dissertation Abstracts International, Volume: 53-11, Section: B, page: 5524. / Major Professor: R. N. Mariscal. / Thesis (Ph.D.)--The Florida State University, 1992.