Stony corals (Anthozoa: Scleractinia) of Burdwood Bank and neighbouring areas, SW Atlantic Ocean

The presence of ten species of stony corals was recorded at a total of 19 out of 48 sampling stations at Burdwood Bank and neighbouring areas. Scleractinians were recorded only at three stations inside the marine protected area (MPA) Namuncurá I, while the majority of them were recorded deeper than 200 m. Burdwood Bank slope (MPA Namuncurá II + NW slope) was the richest sub-area, with ten species recorded in the present study and another two species mentioned from the literature. For the majority of the species the results here presented represent the only available data in the study area after 50 years (or more), comprising updates of latitudinal and bathymetric ranges. Stony corals were recorded as basibionts of a variety of organisms. Mainly dead skeletons were found providing a suitable settlement substrate for sessile species such as primnoid corals. The presence of a high richness of stony corals on the southern slope of Burdwood Bank, as components of the marine animal forests recorded, also supported the conservation efforts made to create the new MPA named “Namuncurá/Burdwood Bank II” in this region.

Chaetopterus antarcticus (Polychaeta: Chaetopteridae) in Argentinian shelf scallop beds: from infaunal to epifaunal life habits

ABSTRACT. Introduction: The shelf-break frontal area in the Argentine Sea, between 37º S and 40º S, is characterized by high frequency and abundance of the parchment worm Chaetopterus antarcticus Kinberg, 1866 associated to Zygochlamys patagonica scallop beds. This polychaete was usually collected within its U tubes, typical of infaunal habit. During 2007, a surprising massive settlement of worms on scallops was observed. Objective: Our objectives is to report the variability of life habits of C. antarcticus in scallop grounds distributed between 37º S and 40º S in Argentinean waters. Methods: The presence of the parchment tube worms on Z. patagonica was analyzed in 892 scallops coming from three samples collected in September (previously obtained for other purposes) and November 2007 and April 2008, between 99-106 m depth in Management Unit B (16.186 km2, 38º S - 39º 52’ S). Polychaetes were identified and quantified on both valves. In addition, both epibiont and infaunal worms were registered through time. The settlement of C. antarcticus on scallops was monitored during the period 2007-2015 and the presence of free tubes, both empty and inhabited by worms, were registered during the period 2008-2015 from a total of 374 representative subsamples (10 l) collected with trawling tools between 37º S and 40º S. Results: Scallops collected in 2007 and 2008 showed that 468 (> 50 %) specimens were encrusted; in 66 % (311 specimens) of them C. antarcticus was settled. The temporal analysis showed that the spatial distribution of epibiotic worms decreased in 2009, 2010 and 2012, with its total absence in 2013, 2014 and 2015 in the study area. During the period 2007 - 2015, infaunal worms were registered throughout the area, collected in part of the locations monitored. Conclusions: The variability of life habits of C. antarcticus was not commonly registered previously in the study area; epibiotic behavior could be the result of intensive soft sediment disturbance due to trawling and hence, the selection of other available primary settlement substrate.

PREFERENSI PENEMPELAN, PERTUMBUHAN, DAN SINTASAN LARVA TERIPANG PASIR, Holothuria scabra PADA SUBSTRAT LAMUN YANG BERBEDA

Teripang pasir, Holothuria scabra merupakan komoditas hasil laut yang bernilai ekonomis tinggi. Penangkapan berlebihan stok di alam mendorong berkembangnya kegiatan budidaya. Penempelan merupakan fase kritis pada larva teripang karena terjadi peralihan sifat planktonis ke bentik yang memerlukan substrat. Penelitian ini bertujuan untuk mengetahui preferensi penempelan, pertumbuhan, dan sintasan larva H. scabra fase penempelan pada substrat lamun yang berbeda. Penelitian menggunakan metode rancangan acak lengkap dengan perlakuan empat jenis daun lamun berbeda dan lima ulangan. Perlakuan terdiri atas Enhalus acoroides (L-1), Syringodium isoetifolium (L-2), Cymodocea serrulata (L-3), dan Cymodocea rotundata (L-4). Jumlah awal larva sebanyak 1.000 individu dan substrat dirangkai dengan luasan yang sama sebesar 12 cm x 17 cm untuk setiap unit penelitian. Hasil penelitian menunjukkan jenis lamun yang digunakan sebagai substrat berpengaruh secara nyata terhadap preferensi penempelan dan sintasan larva teripang pasir, namun tidak berpengaruh terhadap pertumbuhan. E. acoroides menunjukkan hasil terbaik dengan preferensi penempelan 0,26 ind. cm-2 dan sintasan 10,66%; sehingga layak digunakan sebagai substrat penempelan dalam pembenihan teripang pasir, H. scabra.Holothuria scabra larvae on different seagrass substrates. By: Lisa Fajar Indriana, Yuli Afrianti, Sitti Hilyana, and Muhammad FirdausSandfish Holothuria scabra is marine commodities with a high economic value. Overfishing of natural stocks has compelled an interest to begin aquaculture practice. Settlement is a critical phase for the planktonic larvae as they will transform to benthic form in the presence of substrate. This study aims to evaluate the settlement preferences, growth, and survival rate of H. scabra larvae settled on different seagrass leaves. The research was conducted using the Completely randomized design with four different species of seagrass leaves and five replications. The treatments consist of Enhalus acoroides (L-1), Syringodium isoetifolium (L-2), Cymodocea serrulata (L-3), and Cymodocea rotundata (L-4). Initial number of larvae was 1,000 individuals and the substrate was set with same widthof 12 cm x 17 cm for each unit. Results of the experiment indicated that settlement preference and survival rate of H. scabra larvae was significantly affected by seagrass used as substrate while no significantly differences was observed for growth of larvae. E. acoroides showed the best result with 0.26 ind. cm-2 settelement preference and 10.66% survival rate, so that suitable to be used as settlement substrate in H. scabra hatchery.

Early post-settlement mortality of the scallop Pecten fumatus and the role of algal mats as a refuge from predation

Early post-settlement mortality is one of the main processes determining distribution and abundance patterns of marine benthic invertebrates. Most scallops have an attached phase as spat before they release the byssus and move onto the soft sediments. Thus, spat differ from other stages of life in their use of microhabitat, lack of mobility, and therefore in their vulnerability to mortality processes such as predation. However, the contribution of predation to explain levels of mortality experienced by spat and early juvenile scallops is unknown. Complex habitats such as seagrasses and algae provide a substrate upon which spat can attach and might confer an advantage as a refuge from predation. This study investigates the contribution of early post-settlement predation on abundance of Pecten fumatus and determines the role of the algae Hincksia sordida as a refuge from predation. Data were collected using field observations, a predator exclusion experiment, and tethering techniques. Mortality of up to 85% during the first weeks after settlement appeared to have prevented the establishment of an adult population at our study site. Mats of the macroalgae H. sordida provided a settlement substrate for P. fumatus spat. However, increased algal biomass did not provide greater protection from predation to juvenile scallops than lower algal biomass. Our study suggests that prey survival in submersed vegetation is likely to be dynamic among years, and affected by prey behaviour and density as well as the characteristics of the submerged vegetation.

Settlement, growth and survival of eastern oysters on alternative reef substrates

Restoration of the native eastern oyster (Crassostrea virginica) has been severely hindered by the dwindling supply and rising costs of fossil and new oyster shell for use in reef restoration. Consequently, emphasis has shifted to the use of alternative oyster reef materials, which need to be tested for their effectiveness as settlement substrate. Furthermore, low recruitment of wild larvae has also impeded restoration, indicating a need to assess the potential of field setting of cultured larvae. We experimentally examined oyster settlement, growth and survival on unconsolidated oyster shell, oyster shell embedded vertically in concrete, and concrete Oyster Castles® in field and mesocosm experiments. In addition, we examined settlement success of cultured larvae in the mesocosm experiment. In the field experiment, juvenile recruitment was 3x higher on castles and unconsolidated shell than on embedded shell. Castles retained 4x the number of oysters and hosted 5x the biomass than embedded shell, and retained 1.5x the oysters and hosted 3x the biomass than unconsolidated shell. The proportion of live oyster recruits on castles was 1.5x that on both embedded and unconsolidated shell. In the mesocosm experiment (90-d post-larval deployment), the castles recruited, retained, and hosted an oyster biomass 4x higher than that of unconsolidated and embedded shell. This study confirms that artificial reef materials such as Oyster Castles® are suitable alternative substrates for oyster restoration, and remote setting of larvae onto conditioned substrate can be effective under controlled environmental conditions. Future restoration efforts should consider use of alternative reef substrates and field setting of larvae to maximize oyster recruitment, while simultaneously minimizing the cost of reef restoration.

Variability in epibiont colonization of shells of Fusitriton magellanicus (Gastropoda) on the Argentinean shelf

An inventory of the main epibiont organisms on living specimens, on empty shells and on pagurized shells of Fusitriton magellanicus collected in Zygochlamys patagonica fishing grounds off Argentina is provided here. Additionally, considering that the presence of the thick, hairy periostracum could be an inhibitor of boring and encrusting species, we analyse the presence of a periostracum in living F. magellanicus in relation to the presence of epibionts. More than 70% of all shells bore encrusting organisms (of at least 30 taxa) but only a small proportion of shells was heavily fouled, the majority of living, empty and pagurized shells being lightly or moderately fouled. Polychaetes were the most common epibiont group (present on more than 60% of shells) while sponges and ascidians were responsible for the majority of the heavily fouled living gastropods. In general, specimens had a moderate level of encrustation and, simultaneously, a low or medium coating of periostracum. Hairy gastropods (only 14% of the sampled specimens) had few or no epibionts. A relationship between the size of the shell and the level of encrustation was only found in living gastropods. Fusitriton magellanicus is the second species in importance (after the Patagonian scallop) for the provision of a hard settlement substrate in the shelf-break frontal area of the Argentine Sea.