Shallow Hard Bottoms Research Articles

Diversity and ecology of crustaceans from shallow rocky habitats along the Mediterranean coast of Egypt

Spatio-temporal patterns of the distribution of crustaceans from shallow hard bottoms along the Alexandria coast (Egypt, Mediterranean Sea) were studied during a complete year cycle and also in relation to potential drivers of change (both biotic and abiotic), including variation in habitat-forming species. Overall, the crustacean assemblages appeared poor, including only 14 species belonging to Amphipoda (five species), Isopoda (five species), Tanaidacea (two species), Cirripedia and Decapoda (one species each). The distribution patterns of crustacean assemblages appeared significantly variable both in the spatial and in the temporal dimension on a rather unpredictable basis, albeit variation was related to changes in dominant algal and invertebrate habitat formers. High variability and low species richness observed suggest that the analyzed assemblages are selected by local unfavorable environmental conditions. In fact, the crustacean hard bottom fauna is composed by a bulk of tolerant forms, including the dominant Tanais dulongi, Apohyale perieri, Dynamene bidentata, Sphaeroma serratum, Elasmopus pectenicrus, and Jassa marmorata. Their spatio-temporal dynamics, as well as those of the remaining species, and correlations with the variation of habitat formers and environmental variables are reported. This is a baseline assessment of the crustacean diversity along the Mediterranean coast of Egypt, thus having paramount importance for understanding the predicted future changes of biodiversity for the area.

Marine soundscape as an additional biodiversity monitoring tool: A case study from the Adriatic Sea (Mediterranean Sea)

Acoustic monitoring can provide essential information on marine environments, including insights into ecosystem functioning and marine biodiversity monitoring. However, data on species acoustic behavior and ecoacoustics studies in the Mediterranean Sea are still extremely scarce and this limits our ability to use soundscape features in monitoring studies. Here we present the results of a soundscape investigation conducted on shallow hard bottoms of the Adriatic Sea (Central Mediterranean basin). We report the presence of diverse circadian rhythms recorded in two different months, July and September. A power spectral density (PSD) was used to assess the overall spectral composition over time, and the Acoustic Complexity Index (ACI), was identified as a proxy for marine sounds of biological origin. The dominant component of the biological soundscape was composed of snapping shrimps and fishes. Spectral characteristics varied significantly both daily and between the two months. For frequencies >620Hz (i.e., associated to snapping shrimp activity), both PSD and ACI were higher in July than in September. The same circadian rhythm was reported in both sampling periods, with the presence of snaps for 24h a day, but with significantly lower intensity during daylight hours and pitches at the beginning and ending of the night. At lower frequencies (i.e., <620Hz), fish vocalizations mostly occurred during the night. Higher values of ACI were recorded during the night in both months, whereas the presence of anthropogenic noise caused opposite results in PSD levels. Noise was associated with higher PSD and ACI at the peak frequency of the snaps, suggesting a stimulation in snapping activity. Our findings provide new insights on the marine biological soundscape and on the potential use of ecoacoustics in future monitoring programs.

Distribution patterns of shallow water polychaetes (Annelida) along the Alexandria coast, Egypt (eastern Mediterranean)

Shallow hard bottom and intertidal soft bottom polychaete assemblages of the Alexandria coast, southeastern Mediterranean (Levantine Sea), were studied during a complete annual cycle in order to analyze spatial temporal patterns of variation in assemblages, and relevant factors related to polychaete distribution. The present study recorded a total of 73 species, belonging to Syllidae (22 species), Nereididae (9 species), Serpulidae (6 species), Eunicidae (5 species) and other 19 families. The assemblages experienced pronounced spatial and temporal variation throughout the study area, but spatial variation appeared more important in determining the observed patterns. Polychaete distribution related to variation of grain size and sessile macrobenthos cover suggesting that these structural variables accounted more than the physical-chemical ones (namely BOD, dissolved oxygen, organic carbon, organic matter, salinity, temperature, pH) in influencing the patterns of assemblages’ distribution. The present study is the southeastern-most one dealing with ecology and distribution patterns of hard bottom polychaetes from the Mediterranean Sea, as well as one of the few studies dealing with intertidal soft bottom polychaetes in the Levant Basin.

Predation on the toxic zoanthid Palythoa caribaeorum by reef fishes in the abrolhos bank, eastern Brazil

Marine Program, Conservation International Brasil (Rua das Palmeiras, 451, 45900-000 Caravelas, BA, Brasil) E-mail: r.moura@conservation.org.br Palythoa caribaeorum is a common zoanthid that occurs on shallow hard bottoms throughout the Western Atlantic from southern Florida to southern Brazil. It is characterized by possessing the highest growth rate among the anthozoans (up to 4 mm./day

Prediction and validation of flow-dependent uptake of ammonium over a seagrass-hardbottom community in Florida Bay

Hydrodynamic surveys and field flume experiments were carried out to characterize water flow and measure nutrient uptake over a shallow hardbottom flat sparsely colonized by sea- grasses, a complex community type commonly found along corridors linking Florida Bay and the Florida reef tract. Acoustic Doppler velocimeter profiles collected in tide-driven flows revealed ben- thic hydrodynamic conditions indicative of disturbed boundary layer flow; attenuation of flow near the benthos and measures of bottom friction were considerably less than observed in densely colo- nized seagrass beds. Mass-transfer coefficients (S) for ammonium, predicted using velocity data and estimates of bottom friction, ranged between 0.35 × 10 4 and 1.91 × 10 4 m s -1 for current velocity between 0.03 and 0.39 m s -1 . Values of S measured using a field flume were within the same range as predicted values, validating that ammonium uptake by the community is occurring near the mass- transfer limit. Mass-transfer coefficients fell slightly above those previously measured for low-relief coral rubble and below those for dense seagrass canopies, thereby confirming a close link between bottom roughness and mass transfer. Predicted ammonium uptake based on ambient velocity and nutrient concentrations varied considerably over the tidal cycle (range = 0.014 to 0.094 µmol NH4 m -2 s -1 ) and highlighted the importance of temporal variation in both current velocity and nutrient con- centration in driving rates of nutrient uptake. Additional field flume experiments using 15 N-labeled ammonium enabled us to examine flow-dependent uptake for a number of organisms within the com- plex community. Uptake rates were found to vary among seagrasses, macroalgae, and finger corals, perhaps due to physiological or morphological differences or varying locations within the canopy.

LAND ACQUISITION AS A RESTORATION ALTERNATIVE: AN EXAMPLE FROM THE BARGE BERMAN OIL SPILL IN PUERTO RICO

ABSTRACT The Morris J Berman oil spill was a large and significant spill occurring at the height of the tourist season in San Juan, Puerto Rico in January 1994. Two major categories of injury were compensated through a single land acquisition project. Restoration for lost recreational beach use was wholly compensated with the land acquisition project. The eolianite reef injury was mostly satisfied by the same land acquisition restoration project, but with the addition of two other restoration projects. Creating new recreational beach use opportunities by acquiring privately owned coastal habitat was a natural choice for restoration. Demonstrating the resource service link between a variety of coastal habitats and eolianite habitat was more challenging. The Trustee Council undertook a Habitat Suitability Analysis to demonstrate this service linkage. The Habitat Suitability Analysis (HSA) showed that habitats different from eolianite reef, including seagrass, mangroves and shallow hard-bottom, could provide habitat services to biota that rely upon eoliniate habitat for some part of their life cycle. The land acquired contained a variety of coastal habitats including mangroves, herbaceous wetlands, the mouths of two coastal rivers, the Sabana and Pitahaya Rivers, and reef communities immediately offshore. Additionally, the beach habitat on the parcel was identified in both the Leatherback and Hawksbill Sea Turtle Recovery Plans as being important conservation targets thus increasing their ecological importance. After selecting land acquisition as a restoration alternative, the need to identify a seasoned land acquisition partner was apparent given the intense demand and competition for a limited resource such as coastal land in Puerto Rico. Finding the right partner to assist in land acquisition, as well as engaging the public early were key elements in the success of this restoration alternative. Strategies and recommendations for other Trustees considering land acquisition as a restoration alternative are explored as well as the pitfalls and lessons learned.

독도 연안 암반에 서식하는 초대형 저서동물의 수직분포와 산업종의 현존량 추정

Distribution and stock assessment of mega-benthos living in the shallow hard bottom around Dokdo were studied in July,2000. Depth and topographical conditions have affected to the densities and biomass of benthic animals. In shallow area, less than 10 m depth, turbo shell Batillus cornutus, mussel, Mytilus corusucs were dominated and showed distinct patterns in vertical distribution. On the other hand, the area over 10m depth, it showed diverse pattern depending on topography. Turbo shell, mussel and sea cucumber Stichopus japonicus were dominated in terms of fishery resources, but abalones were rarely sampled. Stock assessment were estimated to be 6.54 M/T, 3.89 M/T and 8.92 M/T, respectively. Some parts of coastal hard bottom around Dokdo, such as the area between Dongdo and Seodo, seemed to play an Important role as nursery ground. Therefore, it is necessary to the environmental monitoring for coastal fishery managements aspects.

Benthic associations of the shallow hard bottoms off Terra Nova Bay, Ross Sea: zonation, biomass and population structure

Quantitative and semi-quantitative samples of phyto- and zoobenthic organisms were collected by SCUBA diving at five stations along a depth transect from 0.5–16 m on the shallow hard bottoms off Terra Nova Bay, Ross Sea, Antarctica. The benthic associations were dominated by two macroalgal species (Iridaea cordata and Phyllophora antarctica) and by few animal taxa (mainly polychaetes, molluscs and peracarid crustaceans). Distribution at the community and species levels revealed a well-defined zonation pattern as a function of depth, governed mainly by sea ice scouring and melting. Zonation of vagile fauna was also affected by the effects of covering and architecture of the two dominant macroalgae. Species richness and diversity were higher in the Phyllophora-associated community, where habitat complexity and sheltering were higher. The highest faunal abundance (over 82 000 ind.m−2) and biomass (macroalgae and fauna wet weight 2392 g m−2) were recorded at 2 m depth in association with the Iridaea covering, where the harsher environmental conditions select a few taxa. The biomass values, even if underestimates of the whole community standing crop, are among the highest recorded in shallow austral biotopes. An autoecological and demographic analysis of the most abundant animal species revealed for some species (e.g. Laevilitorina antarctica and Paramoera walkeri) a quite complex population structure with up to three size classes, including juveniles. In some species, the cohort of juveniles showed a well-defined depth preference probably related to sheltering by the macroalgae. As a whole, the species analyzed showed various and contrasting reproductive strategies, despite the fact that the environmental conditions along the transect were relatively similar and quite selective.

The Influence of Temperature, Salinity, and Postlarvai, Transport On the Distribution of Juvenile Spiny Lobsters, Panulirus Argus (Latreille, 1804), in Florida Bay

[Florida Bay is the major nursery for the Caribbean spiny lobster, Panulirus argus, population in south Florida. This region is characterized by a series of shallow hardbottom or seagrass-covered basins separated by carbonate mudbanks that serve as barriers to water circulation and presumably to transport of planktonic larvae. Temperatures fluctuate dramatically in the bay and salinities there range from 35 ppt-50 ppt. In this study, we investigated the physiological tolerance of P. argus postlarvae to various combinations of temperature and salinity representative of the conditions found in Florida Bay and also determined the extent of postlarval recruitment into the interior of the bay. We measured postlarval settlement, juvenile abundances, and postsettlement habitat availability monthly (March 1992-July 1992) along 5 transects extending north from the main Florida Keys into the interior of Florida Bay. Concurrently, P. argus postlarvae were reared in the laboratory, in a completely crossed design, at four temperatures (18°C, 22°C, 29°C and 33°C) and four salinities (25, 35, 45 and 50 ppt). Survival, time:-to-metamorphosis, and growth to the first juvenile stage were measured. Few postlarvae settled at sites beyond the emergent banks ringing Florida Bay, and lobsters were only found in one basin (Twin Keys Basin) where habitat and environmental conditions were favorable. Laboratory results indicate that at high (33°C) and low temperatures (18°C) survival at salinities other than 35 ppt is greatly reduced. Our results indicate that postlarvae are not regularly transported into the interior of Florida Bay and that the lack of suitable nursery habitat and high salinity further limit recruitment, especially at extreme temperatures. Given the present conditions in Florida Bay, recruitment of P. argus is restricted to the southernmost reaches of Florida Bay nearest the Florida Keys., Florida Bay is the major nursery for the Caribbean spiny lobster, Panulirus argus, population in south Florida. This region is characterized by a series of shallow hardbottom or seagrass-covered basins separated by carbonate mudbanks that serve as barriers to water circulation and presumably to transport of planktonic larvae. Temperatures fluctuate dramatically in the bay and salinities there range from 35 ppt-50 ppt. In this study, we investigated the physiological tolerance of P. argus postlarvae to various combinations of temperature and salinity representative of the conditions found in Florida Bay and also determined the extent of postlarval recruitment into the interior of the bay. We measured postlarval settlement, juvenile abundances, and postsettlement habitat availability monthly (March 1992-July 1992) along 5 transects extending north from the main Florida Keys into the interior of Florida Bay. Concurrently, P. argus postlarvae were reared in the laboratory, in a completely crossed design, at four temperatures (18°C, 22°C, 29°C and 33°C) and four salinities (25, 35, 45 and 50 ppt). Survival, time:-to-metamorphosis, and growth to the first juvenile stage were measured. Few postlarvae settled at sites beyond the emergent banks ringing Florida Bay, and lobsters were only found in one basin (Twin Keys Basin) where habitat and environmental conditions were favorable. Laboratory results indicate that at high (33°C) and low temperatures (18°C) survival at salinities other than 35 ppt is greatly reduced. Our results indicate that postlarvae are not regularly transported into the interior of Florida Bay and that the lack of suitable nursery habitat and high salinity further limit recruitment, especially at extreme temperatures. Given the present conditions in Florida Bay, recruitment of P. argus is restricted to the southernmost reaches of Florida Bay nearest the Florida Keys.]