Arthur Ziggiatti Güth

Rhodolith Beds Are Major CaCO3 Bio-Factories in the Tropical South West Atlantic

Rhodoliths are nodules of non-geniculate coralline algae that occur in shallow waters (<150 m depth) subjected to episodic disturbance. Rhodolith beds stand with kelp beds, seagrass meadows, and coralline algal reefs as one of the worlds four largest macrophyte-dominated benthic communities. Geographic distribution of rhodolith beds is discontinuous, with large concentrations off Japan, Australia and the Gulf of California, as well as in the Mediterranean, North Atlantic, eastern Caribbean and Brazil. Although there are major gaps in terms of seabed habitat mapping, the largest rhodolith beds are purported to occur off Brazil, where these communities are recorded across a wide latitudinal range (2°N - 27°S). To quantify their extent, we carried out an inter-reefal seabed habitat survey on the Abrolhos Shelf (16°50′ - 19°45′S) off eastern Brazil, and confirmed the most expansive and contiguous rhodolith bed in the world, covering about 20,900 km2. Distribution, extent, composition and structure of this bed were assessed with side scan sonar, remotely operated vehicles, and SCUBA. The mean rate of CaCO3 production was estimated from in situ growth assays at 1.07 kg m−2 yr−1, with a total production rate of 0.025 Gt yr−1, comparable to those of the worlds largest biogenic CaCO3 deposits. These gigantic rhodolith beds, of areal extent equivalent to the Great Barrier Reef, Australia, are a critical, yet poorly understood component of the tropical South Atlantic Ocean. Based on the relatively high vulnerability of coralline algae to ocean acidification, these beds are likely to experience a profound restructuring in the coming decades.

Extensive Rhodolith Beds Cover the Summits of Southwestern Atlantic Ocean Seamounts

Abstract PEREIRA-FILHO, G.H.; AMADO-FILHO, G.M.; MOURA, R.L.; BASTOS, A.C.; GUIMARÃES, S.M.P.B.; SALGADO, L.T.; FRANCINI-FILHO, R.B.; BAHIA, R.G.; ABRANTES, D.P.; GUTH, A.Z., and BRASILEIRO, P.S., 2012. Extensive rhodolith beds cover the summits of southwestern Atlantic Ocean seamounts. Calcium carbonate production by marine organisms is an essential process in the global budget of , and coralline reefs are the most important benthic carbonate producers. Crustose coralline algae (CCA) are well recognized as the most important carbonate builders in the tropical Brazilian continental shelf, forming structural reefs and extensive rhodolith beds. However, the distribution of CCA beds, as well as their role in mineralization in mesophotic communities and isolated carbonate banks, is still poorly known. To characterize the bottom features of several seamount summits in the Southwestern Atlantic (SWA), side-scan sonar records, remotely operated vehicle imagery, and benthic samples with mixed-gas scuba diving were acquired during two recent research cruises (March 2009 and February 2011). The tops of several seamounts within this region are relatively shallow (∼60 m), flat, and dominated by rhodolith beds (Vitória, Almirante Saldanha, Davis, and Jaseur seamounts, as well as the Trindade Island shelf). On the basis of abundance, dimensions, vitality, and growth rates of CCA nodules, a mean CaCO3 production was estimated, ranging from 0.4 to 1.8 kg m−2 y−1, with a total production reaching 1.5 × 10−3 Gt y−1. Our results indicate that these SWA seamount summits provide extensive areas of shallow reef area and represent 0.3% of the worlds carbonate banks. The importance of this habitat has been highly neglected, and immediate management needs must be fulfilled in the short term to ensure long-term persistence of the ecosystem services provided by these offshore carbonate realms.

Reef fish and benthic assemblages of the Trindade and Martin Vaz Island group, southwestern Atlantic

The Trindade and Martin Vaz island group (TMVIG) is located at about 1,120 km off the Brazilian coast. Despite its importance, highlighted by the presence of several endemic fish species, the TMVIG lacks detailed information on the structure of fish and benthic assemblages. Presented here is the first quantitative assessment of reef fish and benthic assemblages of the TMVIG in a depth gradient ranging from 5 to 45 m. Additional qualitative information on reef assemblages between 45 and 100 m was obtained using advanced gas diving techniques (TRIMIX) and a remotely operated vehicle (ROV). Similarly to other Brazilian oceanic islands, the TMVIG possesses depauperated fish and benthic assemblages, possibly due to its isolation and small size in comparison to the mainland. Depth was the most important factor affecting the structure of fish assemblages, with the density of most fish species declining with depth. Deep reefs (> 45 m) were characterized by the presence of extensive rhodolith beds and rocky reefs sparsely covered with crustose coralline algae, black coral (Cirripathes sp.) and a few massive or plate-like reef corals. Part-time or obligatory planktivorous fishes (e.g. Cephalopholis furcifer and Clepticus brasiliensis) also dominated deep reefs. Similar characteristics were recorded in mesophotic reef ecosystems across the Western Atlantic. Evidence of overfishing (obtained here and in other recent studies), the presence of four endemic and restricted range fish species, as well as the increase in number of new (and still undescribed) endemic taxa, indicates that the adoption of precautionary conservation measures are urgently needed in order to maintain the fragile and unique ecosystems of the TMVIG.

Diet and feeding behavior of Kyphosus spp. (Kyphosidae) in a Brazilian subtropical reef

The present study analyzed and compared diet and fe eding behavior (substrate use, position in water co lumn, interactions with other fishes) of Kyphosus spp. (sea chubs) in a Brazilian subtropical reef. Juveniles ( ≤ 160 mm) of Kyphosus incisor consumed both algae and invertebrates, which were mainly calanoid copepods. Juvenile and small adults of also observed foraging in the water column. We thus provide the first record of omnivory for Kyphosids in the southwest Atlantic Ocean.

Production in Giant Clam Aquaculture: Trends and Challenges

ABSTRACT Giant clams are bivalves found across Indo-Pacific coral reefs and intensively harvested for both food and marine aquarium trade markets. Aquaculture protocols are well established, but there is very little data available on production and trade. This review compiled data from several international agencies and from each one of the 20 giant clam farms active in 13 countries in the Indo-Pacific. The findings show that the import/export data do not match, and that approximately 50% of internationally traded clams are aquacultured. Approximately 150,000 individuals were produced in 2015, mostly by private companies targeting the aquarium trade. Government hatcheries produced clams not only for the aquarium trade, but also for restocking and feeding local communities. However, production is still low and only three of the 20 farms collaborate with universities or research institutions and all of them reported production problems related to technical, commercial, infrastructure, and environmental issues. In order to fight such problems and optimize production, it is important that producers, universities, and government agencies throughout the world communicate with each other.

Pressure tolerance of tadpole larvae of the Atlantic ascidian Polyandrocarpa zorritensis: potential for deep-sea invasion

How deep-sea fauna evolved is a question still being investigated. One of the most accepted theories is that shallow water organisms migrated to deeper waters and gave origin to the deep-sea communities. However, many organisms are prevented from performing long vertical migrations by the increasing hydrostatic pressure. Tadpole larvae of the ascidian Polyandrocarpa zorritensis were submitted to pressure treatments of 1, 50, 100 and 200 atm. Survival, settlement and metamorphosis rates were verified after 24 hour incubation in a pressure chamber. The majority of larvae settled (84%, 62%, 83% and 77% respectively) and successfully underwent metamorphosis (93%, 59%, 85% and 60%) in all pressure treatments. Larval mortality was of less than 15% in all treatments, except for the 50 atm treatment, which presented 38% mortality. Nearly 100% of the surviving larvae underwent metamorphosis in the treatments of 1, 50 and 100 atm. However, 1/3 of the individuals were still in their larval stages in the 200 atm treatment and presented delayed development. These data suggest that ascidian larvae can withstand the hydrostatic pressure levels found in the deep-sea. It is therefore feasible that the current abyssal ascidian species may have colonized the deep-sea through vertical migration and in only a few generations.