Understanding temporal patterns of marine mammal occurrence is useful for establishing conservation strategies. We used a 38 yr-long dataset spanning 1976 to 2013 to describe temporal patterns and ...trends in marine mammal strandings along a subtropical stretch of the east coast of South America. This region is influenced by a transitional zone between tropical and temperate waters and is considered an important fishing ground off Brazil. Generalized Additive Models were used to evaluate the temporal stranding patterns of the most frequently stranded species. Forty species were documented in 12,540 stranding events. Franciscana (n = 4,574), South American fur seal, (n = 3,419), South American sea lion (n = 2,049), bottlenose dolphins (n = 293) and subantarctic fur seal (n = 219) were the most frequently stranded marine mammals. The seasonality of strandings of franciscana and bottlenose dolphin coincided with periods of higher fishing effort and strandings of South American and subantarctic fur seals with post-reproductive dispersal. For South American sea lion the seasonality of strandings is associated with both fishing effort and post-reproductive dispersal. Some clear seasonal patterns were associated with occurrence of cold- (e.g. subantarctic fur seal) and warm-water (e.g. rough-toothed dolphin) species in winter and summer, respectively. Inter-annual increases in stranding rate were observed for franciscana and South American fur seal and these are likely related to increased fishing effort and population growth, respectively. For subantarctic fur seal the stranding rate showed a slight decline while for bottlenose dolphin it remained steady. No significant year to year variation in stranding rate was observed for South American sea lion. The slight decrease in frequency of temperate/polar marine mammals and the increased occurrence of subtropical/tropical species since the late 1990s might be associated with environmental changes linked to climate change. This long-term study indicates that temporal stranding patterns of marine mammals might be explained by either fishing-related or environmental factors.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The western South Atlantic (WSA) humpback whale population inhabits the coast of Brazil during the breeding and calving season in winter and spring. This population was depleted to near extinction by ...whaling in the mid-twentieth century. Despite recent signs of recovery, increasing coastal and offshore development pose potential threats to these animals. Therefore, continuous monitoring is needed to assess population status and support conservation strategies. The aim of this work was to present ship-based line-transect estimates of abundance for humpback whales in their WSA breeding ground and to investigate potential changes in population size. Two cruises surveyed the coast of Brazil during August-September in 2008 and 2012. The area surveyed in 2008 corresponded to the currently recognized population breeding area; effort in 2012 was limited due to unfavorable weather conditions. WSA humpback whale population size in 2008 was estimated at 16,410 (CV = 0.228, 95% CI = 10,563-25,495) animals. In order to compare abundance between 2008 and 2012, estimates for the area between Salvador and Cabo Frio, which were consistently covered in the two years, were computed at 15,332 (CV = 0.243, 95% CI = 9,595-24,500) and 19,429 (CV = 0.101, 95% CI = 15,958-23,654) whales, respectively. The difference in the two estimates represents an increase of 26.7% in whale numbers in a 4-year period. The estimated abundance for 2008 is considered the most robust for the WSA humpback whale population because the ship survey conducted in that year minimized bias from various sources. Results presented here indicate that in 2008, the WSA humpback whale population was at least around 60% of its estimated pre-modern whaling abundance and that it may recover to its pre-exploitation size sooner than previously estimated.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer ...continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern Atlantic.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract The Antarctic Peninsula (West Antarctica) marine ecosystem has undergone substantial changes due to climate-induced shifts in atmospheric and oceanic temperatures since the 1950s. Using 25 ...years of satellite data (1998-2022), this study presents evidence that phytoplankton biomass and bloom phenology in the West Antarctic Peninsula are significantly changing as a response to anthropogenic climate change. Enhanced phytoplankton biomass was observed along the West Antarctic Peninsula, particularly in the early austral autumn, resulting in longer blooms. Long-term sea ice decline was identified as the main driver enabling phytoplankton growth in early spring and autumn, in parallel with a recent intensification of the Southern Annular Mode (2010-ongoing), which was observed to influence regional variability. Our findings contribute to the understanding of the complex interplay between environmental changes and phytoplankton responses in this climatically key region of the Southern Ocean and raise important questions regarding the far-reaching consequences that these ecological changes may have on global carbon sequestration and Antarctic food webs in the future.
Marine plastic pollution has a range of negative impacts for biota and the colonization of plastics in the marine environment by microorganisms may have significant ecological impacts. However, data ...on epiplastic organisms, particularly fungi, is still lacking for many ocean regions. To evaluate plastic associated fungi and their geographic distribution, we characterised plastics sampled from surface waters of the western South Atlantic (WSA) and Antarctic Peninsula (AP), using DNA metabarcoding of three molecular markers (ITS2, 18S rRNA V4 and V9 regions). Numerous taxa from eight fungal phyla and a total of 64 orders were detected, including groups that had not yet been described associated with plastics. There was a varied phylogenetic assemblage of predominantly known saprotrophic taxa within the Ascomycota and Basidiomycota. We found a range of marine cosmopolitan genera present on plastics in both locations, i.e., Aspergillus, Cladosporium, Wallemia and a number of taxa unique to each region, as well as a high variation of taxa such as Chytridiomycota and Aphelidomycota between locations. Within these basal fungal groups we identified a number of phylogenetically novel taxa. This is the first description of fungi from the Plastisphere within the Southern Hemisphere, and highlights the need to further investigate the potential impacts of plastic associated fungi on other organisms and marine ecosystems.
Most current bioexposure assessments for UV filters focus on contaminants concentrations in fish from river and lake. To date there is not information available on the occurrence of UV filters in ...marine mammals. This is the first study to investigate the presence of sunscreen agents in tissue liver of Franciscana dolphin (Pontoporia blainvillei), a species under special measures for conservation. Fifty six liver tissue samples were taken from dead individuals accidentally caught or found stranded along the Brazilian coastal area (six states). The extensively used octocrylene (2-ethylhexyl-2-cyano-3,3-diphenyl-2-propenoate, OCT) was frequently found in the samples investigated (21 out of 56) at concentrations in the range 89–782 ng·g–1 lipid weight. São Paulo was found to be the most polluted area (70% frequency of detection). Nevertheless, the highest concentration was observed in the dolphins from Rio Grande do Sul (42% frequency of detection within that area). These findings constitute the first data reported on the occurrence of UV filters in marine mammals worldwide.
Although marine plastic pollution has been the focus of several studies, there are still many gaps in our understanding of the concentrations, characteristics and impacts of plastics in the oceans. ...This study aimed to quantify and characterize plastic debris in oceanic surface waters of the Antarctic Peninsula. Sampling was done through surface trawls, and mean debris concentration was estimated at 1,794 items.km
with an average weight of 27.8 g.km
. No statistical difference was found between the amount of mesoplastics (46%) and microplastics (54%). We found hard and flexible fragments, spheres and lines, in nine colors, composed mostly of polyurethane, polyamide, and polyethylene. An oceanographic dispersal model showed that, for at least seven years, sampled plastics likely did not originate from latitudes lower than 58°S. Analysis of epiplastic community diversity revealed bacteria, microalgae, and invertebrate groups adhered to debris. Paint fragments were present at all sampling stations and were approximately 30 times more abundant than plastics. Although paint particles were not included in plastic concentration estimates, we highlight that they could have similar impacts as marine plastics. We call for urgent action to avoid and mitigate plastic and paint fragment inputs to the Southern Ocean.
Toothed cetaceans represent a diverse and important component in poorly studied pelagic food webs. We used the variation in δ
13
C and δ
15
N values in tooth dentin and bone collagen sampled from 185 ...specimens of 23 species (families Delphinidae, Physeteridae, Kogiidae, Phocoenidae, and Ziphiidae) stranded in the western South Atlantic Ocean (WSAO) to estimate the isotopic niche width and assess the interspecific isotopic niche overlap. Two gradients of increasing δ
13
C values among species were evidenced: ocean-coast and high-to-low latitudes. Variation in δ
13
C and δ
15
N values indicated the existence of at least four trophic and habitat-related guilds: neritic high trophic-level predators (
Pseudorca crassidens
,
Tursiops truncatus gephyreus
,
T. truncatus truncatus
and
Phocoena spinnipinis
); oceanic intermediate trophic-level predators (
Orcinus orca
,
Steno bredanensis
,
Kogia breviceps
,
Lagenodelphis hosei
,
Physeter macrocephalus
,
Delphinus delphis
and
Stenella frontalis
), oceanic low trophic-level predators (
Grampus griseus
,
P. crassidens
—mass stranded group,
Mesoplodon grayi
,
M. densirostris
,
Ziphius cavirostris
,
Globicephala melas
,
S. coeruleoalba
, and
K. sima
), all from the subtropics, and a temperate/polar grouping of neritic/oceanic low trophic-level predators (
Berardius arnuxii
,
M. layardii
,
M. hectori
and
P. dioptrica
). Furthermore, our results also suggest the occurrence of putative ecotypes of
O. orca
and
P. crassidens
. The isotopic niche width was highly variable among species, with high niche overlap among several oceanic taxa. The results of the present study suggest a wide variation in trophic position, habitat and, therefore, the ecological role of different odontocete species in the WSAO ecosystems.
Genetic data have become an important asset to enhance the delimitation of cetacean species, subspecies, and populations, considering the difficulties in obtaining representative morphological data. ...The franciscana,
Pontoporia blainvillei
(Gervais & d’Orbigny
1844
), is the most threatened small cetacean in the southwestern Atlantic Ocean. Genetic studies have shown a deep genetic divergence between franciscanas from the northern and southern parts of the range; thus, it was proposed that they should be considered two Evolutionarily Significant Units (ESU). Morphological and ecological data also suggest differences across the species range. We used genetic data from samples collected throughout the species distribution (N = 399) to test hypotheses of intraspecific differentiation that could reflect the existence of subspecies within
P. blainvillei
. We applied the divergence and diagnosability criteria for recognition of cetacean subspecies, based on mitochondrial control region sequences. The net between-group nucleotide divergence (
d
A
= 0.0074) and the percent diagnosable (99%) indicate that the franciscana’s North and South ESU meet the criteria to be recognized as subspecies. Morphological and ecological evidence also support the two subspecies claim. Therefore, we propose a trinomial and provide diagnoses for the new subspecies.
Stomach contents of South American (Arctocephalus australis) (n = 219) (SAFS) and sub‐Antarctic (A. tropicalis) (n = 37) (SFS) fur seals were opportunistically sampled from 1980 to 2021 to examine ...their feeding habits and resource partitioning in southern Brazil while in their nonreproductive periods. SAFSs mainly consumed abundant coastal pelagic species, such as Anchoa marinii and Doryteuthis sanpaulensis, resulting in high sexual trophic niche overlap. The frequency of occurrence (%FO) of fish prey, especially the overexploited Micropogonias furnieri, decreased between 1980–1992 and 2007–2021, while squid increased. For SFSs, offshore squids such as Ommastrephes bartramii and Illex argentinus were the most important prey considering both sexes in the long‐term. The interspecific trophic niche overlap was low, but it is likely underestimated since it increased with the inclusion of scat samples from SFSs. This sample‐size effect was also observed in Shannon's diversity index, which was lower for underrepresented SFSs. Marine debris ingestion was detected in both species (SAFS %FO = 2.7; SFS %FO = 8.3), with only flexible plastic material found. This study brings novel information on feeding habits of fur seal species in the extreme south of Brazil, as well as unprecedented information about their ecology during the nonreproductive period.
Resumo
Conteúdos estomacais de lobos‐marinhos‐do‐sul (Arctocephalus australis) (n = 219) e lobos‐marinhos‐subantárticos (A. tropicalis) (n = 37) foram oportunisticamente amostrados entre 1980 e 2021 para avaliar seus hábitos alimentares e compartilhamento de recursos no sul do Brasil durante o período não‐reprodutivo. O lobo‐marinho‐do‐sul consumiu principalmente recursos costeiros pelágicos abundantes, como Anchoa marinii e Doryteuthis sanpaulensis, com alta sobreposição de nicho trófico entre os sexos. A nível populacional, a frequência de ocorrência (%FO) de peixes, especialmente da sobreexplorada Micropogonias furnieri, diminuiu entre 1980–1992 e 2007–2021, enquanto a de lulas aumentou. Para o lobo‐marinho‐subantártico, lulas oceânicas como Ommastrephes bartramii e Illex argentinus foram as presas mais importantes considerando ambos os sexos a longo‐prazo. A sobreposição de nicho trófico entre as espécies foi baixa, mas provavelmente subestimada, uma vez que ela aumentou quando alguns conteúdos fecais dos lobos‐marinhos‐subantárticos foram considerados. O mesmo efeito do número amostral foi observado no índice de diversidade de Shannon, o qual foi menor para o lobo‐marinho‐subantártico. Ingestão de resíduos sólidos antropogênicos foi detectada em ambas as espécies (Lobo‐marinho‐do‐sul %FO = 2,7; Lobo‐marinho‐subantártico %FO = 8,3) e somente material plástico flexível foi encontrado. Esse estudo é o primeiro a avaliar os hábitos alimentares de lobos‐marinhos de maneira quantitativa no extremo sul do Brasil, e traz informações sem precedentes sobre sua ecologia fora das colônias reprodutivas.
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