Rocas Atoll Research Articles

Population origin and historical demography in hawksbill (Eretmochelys imbricata) feeding and nesting aggregates from Brazil

We studied hawksbills from Brazilian feeding aggregates and nesting colonies to ascertain the origin and genealogical relationship of individuals in the largest southern Atlantic remnant population by using sequences of the mitochondrial (mtDNA) control region and five autosomal genes. A phylogeographic analysis of 246 hawksbills showed four distinct mtDNA haplogroups in the feeding grounds, while only one was found in Brazilian rookeries. We found significant differences among nesting sites in Brazil, and among them and other rookeries worldwide. Differences among Brazilian feeding aggregation sites and others around the world were also found. We were able to show that hawksbills from feeding aggregates at the Brazilian islands of Fernando de Noronha and Rocas Atoll were mainly derived from Brazilian and Caribbean rookeries, although some were related to individuals from the eastern Atlantic and Indo-Pacific, indicating large transoceanic migrations for this species. The nuclear data presented no structure and no signal of demographic change. Mixed stock analyses indicated that Brazilian rookeries contribute mostly to Brazilian feeding grounds, and in a smaller proportion to feeding aggregations in the Caribbean and eastern Atlantic. Finally, hybrids found frequently in rookeries of the Bahia State are not present in the feeding grounds, and thus, may display different feeding and migratory behaviors.

A new species of Cymadusa Savigny, 1816 (Crustacea: Amphipoda: Ampithoidae) from northeastern Brazil

A new species of the amphipod family Ampithoidae Stebbing, 1899 is described from the northeastern Brazilian waters. The new described taxon is grouped in the genus Cymadusa Savigny, 1816, since it presents all the diagnostic characteristics of the genus. The examined material was collected by scuba diving in the Rocas Atoll, off Rio Grande do Norte state coast, Camamu Bay and Todos os Santos Bay, Bahia state. The new species described here is close to C. filosa Savigny, 1816, type species of the genus, by presenting anterior margin of gnathopod 1 poorly setose, male gnathopod 2 densely setose, with palmar corner not defined by a spine and dactylus subequal in length to palm, being considered part of the C. filosa complex. Among the species of this complex, the one which most resembles to the new taxon is C. imbroglio Rabindranath, 1972, which is distinguished by the absence of both the trapezoid process in the palm and spine at the palmar corner in the gnathopod 2. This is the second species of the genus Cymadusa recorded from Brazilian waters.

History, distribution, and seasonal abundance of the Least Tern Sternula antillarum (Aves: Charadriiformes: Sternidae) in Brazil

We review existing data on the distribution of the Least Tern, Sternula antillarum along the Brazilian coast, based on the literature and museum specimens, and present results of a year-long study (October 2008 to September 2009) on the seasonal abundance of this species on a large tidal flat area, Cajuais Bank, in the State of Ceara, north-eastern Brazil. We evaluate whether the observed variation in the abundance of terns is due to the occurrence of an undocumented breeding colony, or alternatively, whether it results from an influx of migrants from the Northern Hemisphere. The recovery of historical data revealed that all literature references on the distribution of birds in the Americas, published up to the late 1990s include Brazil in the non-breeding range of the Least Tern. This inclusion is based on a few, old (late 19th and early 20th centuries) museum specimens, all of which have been collected on the northern and north-eastern coasts of this country'. From the late 1980s, birds continued to be occasionally recorded along the coastline, running from the State of Amapa (01°N) up to the State of Bahia (10°S), with records of single individuals in south-eastern and southern Brazil. An alleged record from Rocas Atoll, 260 km off the Brazilian mainland, might tentatively refer to the Old World Little Tern S. albifrons. At Cajuais Bank, Least Terns occurred from October 2008 to April 2009, and in September 2009. The highest numbers (> 800 individuals) were recorded in January-February (Southern Hemisphere's summer). The species was observed in rather small numbers (< 30) in March-April (early-mid Southern Hemisphere fall) and in September (early Southern Hemisphere spring), being absent from the area in May-August (Southern Hemisphere's fall and winter). In October-December 2008 (Southern Hemisphere's spring), and September 2009 (early Southern Hemisphere's summer), no birds were in breeding plumage. In January, about 32% of the birds were in breeding plumage, while from February-April (Southern Hemisphere's summer to mid fall) all were in breeding plumage. This pattern is consistent with what would be expected for migratory birds. The Cajuais Bank itself (and adjacent beaches and inland environments) holds the largest numbers of Least Terns recorded in Brazil, thus being one of the most significant sites along the migratory route of the species.

Deep Chlorophyll Maximum in Western Equatorial Atlantic - How does it Interact with Islands Slopes and Seamounts?

This paper investigates the dynamics of the deep chlorophyll maximu m layer (DCM L) along the Fernando de Noronha Ridge in the oligotrophic western equatorial Atlantic off northeast Brazil. M ixing processes between water masses above and below the thermocline may occur in a scale of tens of meters around the 24.5 to 25.5 isopycnals, where photoau- totrophs are concentrate at the bottom of the euphotic zone. The primary production at the DCM L can provide 210 (±170) metric tons of Carbon per day to the benthic community at the Rocas atoll. The behavior of isopycnals in deeper and strongly stratified waters suggest that internal waves may imp rove primary production, by lift ing the deeper and nutrient-rich South Atlantic Central Water upwards and carrying the autotrophs to brighter depths.

The effects of sea surface temperature anomalies on oceanic coral reef systems in the southwestern tropical Atlantic

In 2010, high sea surface temperatures that were recorded in several parts of the world and caused coral bleaching and coral mortality were also recorded in the southwest Atlantic Ocean, between latitudes 0°S and 8°S. This paper reports on coral bleaching and diseases in Rocas Atoll and Fernando de Noronha archipelago and examines their relationship with sea surface temperature (SST) anomalies recorded by PIRATA buoys located at 8°S30°W, 0°S35°W, and 0°S23°W. Adjusted satellite data were used to derive SST climatological means at buoy sites and to derive anomalies at reef sites. The whole region was affected by the elevated temperature anomaly that persisted through 2010, reaching 1.67 °C above average at reef sites and 1.83 °C above average at buoys sites. A significant positive relationship was found between the percentage of coral bleaching that was observed on reef formations and the corresponding HotSpot SST anomaly recorded by both satellite and buoys. These results indicate that the warming observed in the ocean waters was followed by a warming at the reefs. The percentage of bleached corals persisting after the subsidence of the thermal stress, and disease prevalence increased through 2010, after two periods of thermal stress. The in situ temperature anomaly observed during the 2009–2010 El Nino event was equivalent to the anomaly observed during the 1997–1998 El Nino event, explaining similar bleaching intensity. Continued monitoring efforts are necessary to further assess the relationship between bleaching severity and PIRATA SST anomalies and improve the use of this new dataset in future regional bleaching predictions.

Richness and palaeo-zoogeographical significance of the benthic Ostracoda (Crustacea) from the oceanic Island of Trindade and Rocas Atoll, Brazil

Twenty-one ostracode species from Trindade Island and 23 species from Rocas Atoll are herein recorded. The collective fauna shows low richness and low abundance compared with other oceanic islands. Nevertheless, the presence of tropical pandemic species such as Kotarocythere inconspicua (Brady) and Triebelina sertata Triebel, of the almost exclusively Pacific genus Australimoosella, the Atlanto-Caribbean taxa such as Glyptobairdia coronata (Brady) and Caudites obliquecostatus Bold, together with species typical of the Brazilian shelf, reveals a mixed fauna likely influenced by dispersal of shallow-water taxa between seamounts during Quaternary sea-level lowstands. In contrast to other oceanic islands, endemic ostracode taxa are apparently absent in these two islands. Tenedocythere trindadensis sp. nov., a species also recorded on the Brazilian equatorial shelf, is described and illustrated.

Chromosomal and morphological divergences in Atlantic populations of the frillfin goby Bathygobius soporator (Gobiidae, Perciformes)

Evidence of population fragmentation and speciation processes has been reported for several species of marine fish, including small cryptobenthics forms of Atlantic. Four populations of the frillfin goby Bathygobius soporator, which cover a wide geographical area of the Atlantic coast in North/Northeast Brazil, were cytogenetically analyzed and their morphological patterns compared. Continental populations of this species (denominated MA, RN, and BA) exhibited divergences in morphological and chromosomal characteristics compatible with interpopulation differentiation. However, specimens from Rocas Atoll (RA) displayed notable divergences in these parameters, corroborating molecular data that suggest they are a different species. Furthermore, the RN population showed intrinsic chromosomal markers, revealing a certain level of population structuring. Chromosomal and morphological patterns found confirm the biodiversity of B. soporator, substantiating an evolutionary scenario of population divergences and adaptation to new habitats.

New records of reef fishes (Teleostei: Perciformes) in the Rocas Atoll Biological Reserve, off northeastern Brazil

Six new records of reef fish and a hybrid species are reported from Rocas Atoll, off Rio Grande do Norte State, northeast Brazil. Data on species abundance, distribution of the recorded species in Brazilian oceanic islands, trophic structure, and the occurrence of the hybrid species “Menephorus dubius” are provided.

Green turtle (Chelonia mydas) nesting on Atol das Rocas, north-eastern Brazil, 1990–2008

In this paper, information is presented on green turtle (Chelonia mydas) nesting on Atol das Rocas (Rocas Atoll), north-eastern Brazil. The temporal distribution of nesting events per season, annual number of nests, carapace length of nesting females, clutch size, hatching success, incubation period, internesting interval, clutch frequency, observed reproductive lifespan, and remigration period are reported. The study period included the nesting seasons from 1990 to 2008, but no regular beach monitoring was carried out in 1998 and 1999. Two sorts of methods were applied to the estimation of the annual number of nests in some seasons. Taking into account the estimated annual numbers of nests, the mean annual number of nests in the study period, excluding 1998–1999, was 335 (standard deviation = 139, range = 136–563, N = 17). An analysis of the available data indicates that the average nesting levels at the beginning of the study period (the first five seasons) and at its end (the last five seasons) were roughly the same. The mean curved carapace length of the nesting turtles decreased significantly during the study period, from 115.9 cm in 1990–1992 to 112.9 cm in 2006–2008. Atol das Rocas was established as a federal biological reserve in 1979, but regular sea turtle conservation activities actually started there in 1990. Since that year, the killing of nesting turtles has ceased, nesting activity by the turtles can proceed in an undisturbed fashion, and their clutches can incubate in a protected environment.

The Interplay of Homing and Dispersal in Green Turtles: A Focus on the Southwestern Atlantic

Current understanding of spatial ecology is insufficient in many threatened marine species, failing to provide a solid basis for conservation and management. To address this issue for globally endangered green turtles, we investigated their population distribution by sequencing a mitochondrial control region segment from the Rocas Atoll courtship area (n = 30 males) and four feeding grounds (FGs) in Brazil (n = 397), and compared our findings to published data (n (nesting) = 1205; n (feeding) = 1587). At Rocas Atoll, the first Atlantic courtship area sequenced to date, we found males were differentiated from local juveniles but not from nesting females. In combination with tag data, this indicates possible male philopatry. The most common haplotypes detected at the study sites were CMA-08 and CMA-05, and significant temporal variation was not revealed. Although feeding grounds were differentiated overall, intra-regional structure was less pronounced. Ascension was the primary natal source of the study FGs, with Surinam and Trindade as secondary sources. The study clarified the primary connectivity between Trindade and Brazil. Possible linkages to African populations were considered, but there was insufficient resolution to conclusively determine this connection. The distribution of FG haplotype lineages was nonrandom and indicative of regional clustering. The study investigated impacts of population size, geographic distance, ocean currents, and juvenile natal homing on connectivity, addressed calls for increased genetic sampling in the southwestern Atlantic, and provided data important for conservation of globally endangered green turtles.

Reef Flat Community Structure of Atol das Rocas, Northeast Brazil and Southwest Atlantic

This study was conducted during 1999 to 2002 and addresses the community structure and some ecological aspects of the benthic reef flat assemblages of Atol das Rocas, located offshore the NE brazilian coast. It corresponds to the sole atoll of the SW Atlantic, which characterized by a shallow topography and is almost completely built by coralline algae. The turf forming red macroalgaeDigenea simplexand the crustose corallineHydrolithon pachydermumwere the dominant species of the reef flat. The crustose green macroalgaeDictyosphaeria ocellataand the turf forming red macroalgaeGelidiella acerosawere the subdominant species. Biomass values ofD. simplexwere about twice higher than the other species, pointing out to its relevance in the community structure of this reef zone. Biodiversity indices indicated a high equitability within the few species observed and a relative temporal stability of the community structure. Some local spatial variations were found in the community structure of the reef flat zone, enabling the definition of three subhabitats. The patterns of distribution and abundance of the benthic organisms seem to be related to the environmental conditions of the reef flat, such as low water turbulence, lengthy periods of aerial exposure, and low herbivore pressure.

Population Structure and Growth of Young Lemon Shark, Negaprion brevirostris (Poey, 1868), at the Atol das Rocas Biological Reserve, Brazil

We conducted expeditions (N=16) to the Rocas Atoll Biological Reserve aiming study the lemon shark (Negaprion brevirostris) population. Youn...

First record of Scartella itajobi Rangel and Mendes, 2009 (Perciformes: Blenniidae) from São Pedro e São Paulo Archipelago, Brazil

This article presents the first record of the blenniid Scartella itajobi in the São Pedro e São Paulo Archipelago, located off the state of Rio Grande do Norte, northeastern Brazil. As a result, the species distribution is extended 610 km northeast. The number of species of Blenniidae known to occur in São Pedro e São Paulo Archipelago is three, whereas the number of endemic fish species shared by São Pedro e São Paulo, Fernando de Noronha, and Rocas Atoll now stands at two.

Reef Bioconstructors of Rocas Atoll, Equatorial South Atlantic doi: 10.5007/2175-7925.2011v24n2p37

This study presents a analysis of reef bioconstructors at Rocas Atoll, Northeast of Brazil, sampled in January and February of 2008. The results show the presence of a community made up mainly of calcareous algae (Porolython pachydermum, Sporolython sp., Lythoporella sp., Lythophyllum sp.), corals (Siderastrea stellata, Favia gravida), vermetids (Dendropoma irregular, Petaloconchus varians) and foraminifers (Homotrema rubrum) in the reef formation. This taxonomic survey show the importance of a different species during the carbonate growth process of the only Atoll of the Equatorial South Atlantic.

Aspectos biogeomorfológicos do Atol das Rocas, Atlântico Sul Equatorial

Abstract BIOGEOMORPHOLOGICAL ASPECTS OF ROCAS ATOLL, EQUATORIAL SOUTH ATLANTIC Biogeomorphological analysis and mapping of the reef units in the only Atoll from the Equatorial South Atlantic were held for understanding the dynamics and the importance of ocean reef. The zoning shows the presence of the following environmental compartments: reef front, adjacent bottom, reef margin, reef flat, reef ring, suspended reef, lagoonal reef, intertidal sand deposit, reef pass, pools, puddles of tide and the sand cays. The results show that a variety groups of organisms in Atoll that act in group processes such: control of erosion on sand cays, bioprotection, bioerosion, cementation of biogenic carbonate sand, production of biodetritic sediments and bioconstruction. Such biogeomorphological processes generate some of the unique characteristics of Rocas Atoll.

40Ar-39Ar dating of volcanic rocks from the Fernando de Noronha Archipelago

The Fernando de Noronha Archipelago is situated345 km off the Brazilian coast. In terms of tectonics, thearchipelago is confined to a transform fracture zone. TheFernando de Noronha lineament extends a considerabledistance westward and is traced by the Atol das Rocas, aseamount chain, and occurrences of alkaline magmatismin the continent. According to tectonic conceptions, thisstructure is interpreted as a hotspot track.The universally accepted differentiation of the volcanic rocks of the Fernando de Noronha Archipelago wasproposed by Almeida [1]. According to his data, three formations can be distinguished: Remedios, Quixaba, andSao Jose. The igneous rocks of the Remedios Formationare dominated by phonolites and trachytes. The pyroclastic material was produced by explosive eruptions of phonolitic and trachytic magmas. The rocks of the QuixabaFormation are dominated by intercalating ankaratriteflows and pyroclastic layers of the same composition andlie on an erosion surface. Sedimentary rocks were notfound at the stratigraphic boundary between the Remedios and Quixaba formations. Therefore, the sequence offormation of these complexes cannot be established bygeological methods. The nepheline basanites of Sao JoseIsland were distinguished into a separate formation.Almeida argued that these basanites are younger than theankaratrites of the Quixaba Formation.The dating of igneous rocks from the Fernando deNoronha (FN) Islands is important for the understandingof the magmatic evolution of this hot spot. The K–Ar agesreported by Cordani [2] and Kogarko et al. [3] showedthat the alkali basanites of the Sao Jos e Formation and thetrachytes of the Remedios Formation are the oldest igneous rocks of the archipelago (11.7 ± 0.6 Ma and 11.8–11.7 Ma, respectively). According to the same data, thephonolites of the Remedios Formation are somewhatyounger (9.5–8.6 Ma), and the olivine melanephelinitesof the Quixaba Formation are the youngest rocks. In contrast to this model, Almeida [1] supposed previously thatthe Sao Jose basanites are younger than the Quixabaankaratrites (note that the contact between these rocks islocated below the sea level).The classical K–Ar method ignores the possible presence of excess Ar (i.e., Ar absorbed and accumulated during the existence of the mantle block producing the magmatism of the island, rather than radiogenic Ar formed

Two new species of the family Photidae (Amphipoda: Corophiidea: Photoidea) from Brazilian waters, with description of Rocasphotis gen. nov.

A new species, Photis sarae sp. nov., is herein described from Guanabara Bay, Rio de Janeiro. The new species is similar to the Hawaiian species, Photis hawaiensis Barnard, 1955, and an undescribed species, Photis sp. F (LeCroy 2000), from Biscayne Bay, Florida. Photis sarae sp. nov. can be distinguished from both species in having gnathopod 2 basis with two long setae on posterior margin, palm with only one spine (excluding palmar corner), pereopod 3 anterior margin of merus with long plumose and simple setae, and dactyli of pereopods 5–7 with accessory spine and telson trapezoidal with distal margin concave. Also, Rocasphotis gen. nov. is described based on material collected from Atol das Rocas, which is closely related to the genus Photis and also corresponds to a new species. Rocasphotis gen. nov. mainly differs from Photis in having antenna 1 shorter than antenna 2, peduncular article 1 longer than article 3, accessory flagellum absent, coxae 1–4 with sparse slender setae; lateral cephalic lobe weakly extended and acute distally; eyes large, poorly developed, composed of sparse ommatidia, and partly enclosed in the lobe. A key for all genera of the family Photidae is given.

Sedimentos carbonáticos bioclásticos do Atol das Rocas, Atlântico Sul Equatorial

Atolls are reefs that are both generate from as accumulate of carbonate sediments. The bioclastic carbonates of Rocas Atoll, Northeast of Brazil, were analyzed from surface samples of various environmental compartments. The results show the dominance of calcareous algae bioclasts, foraminiferans and molluscs in sediments of reef bioconstruction and the sediment dynamics of the area. Evidence of allochtonous and autochtonous contributions in the sedimentological composition of atoll and variations in the composition along the windward-leeward gradient are discussed. Unlike other atolls of the planet, the Rocas Atoll present the lagoonal facies with low proportion of total carbonate facies associated with the reef and low frequency of coral bioclasts.

Sedimentos carbonáticos bioclásticos do Atol das Rocas, Atlântico Sul Equatorial

Atolls are reefs that are both generate from as accumulate of carbonate sediments. The bioclastic carbonates of Rocas Atoll, Northeast of Brazil, were analyzed from surface samples of various environmental compartments. The results show the dominance of calcareous algae bioclasts, foraminiferans and molluscs in sediments of reef bioconstruction and the sediment dynamics of the area. Evidence of allochtonous and autochtonous contributions in the sedimentological composition of atoll and variations in the composition along the windward-leeward gradient are discussed. Unlike other atolls of the planet, the Rocas Atoll present the lagoonal facies with low proportion of total carbonate facies associated with the reef and low frequency of coral bioclasts.

Description of cryptic taxa within the Alpheus bouvieri A. Milne-Edwards, 1878 and A. hebes Kim and Abele, 1988 species complexes (Crustacea: Decapoda: Alpheidae)

Alpheus bouvieri A. Milne-Edwards, 1878 and A. hebes Kim and Abele, 1988 are reviewed based on morphological and genetic data. Alpheus bouvieri, previously believed to be distributed in the eastern Pacific and Atlantic, is restricted to the Atlantic populations; the eastern Pacific populations (A. bouvieri sensu Kim and Abele 1988) are assigned to A. javieri n. sp. A second new species, A. agilis n. sp., closely related to the eastern Pacific A. hebes, is described based on recently collected specimens from the eastern Atlantic (São Tomé, Cape Verde) and western Atlantic (Atol das Rocas off northeastern Brazil). The absence of A. agilis n. sp. (or any other representative of the A. hebes clade) in the Caribbean Sea is likely due to a relatively recent (~1–2 my) extinction. Genetic data (COI sequences) indicates that A. bouvieri and A. javieri n. sp., and A. hebes and A. agilis n. sp. diverged approximately 6 and 7.5 mya, respectively, i.e., around 3 my before the final closure of the Isthmus of Panama.