Climate Change Impacts on the Patagonian Shelf Break Front

We characterize long-term trends of sea surface temperature (SST), absolute dynamic topography, and chlorophyll-a (CHL) in the Patagonian shelf break front (SBF) using 27 years (1993–2019) of satellite data. Warming of the Argentinean shelf waters and the southwestward displacement of the Brazil-Malvinas Confluence (BMC) impact the northernmost extension of the SBF. Cooling of the Malvinas Current (MC) and the concurrent warming of the adjacent shelf waters lead to a significant increase of SST gradients along the outer shelf. The southwestward displacement of the BMC implies a similar shift of the SBF. An increase in CHL trend appears to be associated with southerly wind anomalies along the shelf break. We estimate a southward shift of the northernmost penetration of the MC of −0.11 ± 0.076°/decade.Fil: Franco, Barbara Cristie. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Ruiz Etcheverry, Laura Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Marrari, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Piola, Alberto Ricardo. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Matano, R. P.. State University of Oregon; Estados Unido

Trends and variability in local abundances of sailfish Istiophorus platypterus in Pacific waters of Costa Rica: Controls and effects on recreational fisheries

Fishing tourism represents a vital industry in Costa Rica, generating over US$520 million and attracting 150,000 tourists every year. The main objective of this study is to examine trends and variability in local abundances of sailfish Istiophorus platypterus, the main sportfish in Pacific waters of Costa Rica, and quantify the influence of environmental and anthropogenic factors. We compiled and analyzed sailfish information collected from sportfishing operations. Sailfish abundances were examined in relation to environmental conditions and commercial fishing. Timeseries analyses showed significant declining trends in local abundances of sailfish in the southern and central Pacific of Costa Rica over the last decade. Bycatch records from the commercial purse seine fleet operating in Costa Rican waters also show a declining trend in sailfish numbers. On the other hand, commercial landings from the national longline fleet show a significant increase of 108%, on average, over the past decade. Different numerical models indicated that fishing pressure from the national fleet and also sea surface temperature with different time lags affect local abundances of sailfish. While other countries in Central and North America protect sailfish and other species of tourist interest, Costa Rica still allows the landing and sales of billfishes as seafood. The results presented in this study highlight the need to allow for the recovery of local abundances of sailfish and promote the development of the coastal communities that depend on marine tourism as their main source of income

Seasonal and spatial variability in condition of age-0+ Argentine hake Merluccius hubbsi Marini, 1933, in the San Jorge Gulf (Argentina): A bottom-up perspective

In the north Patagonian region of the Argentinean Continental Shelf, the San Jorge Gulf (SJG; 45°‐47°S, 65°30ʹ‐67°30ʹW) is the main nursery ground of age‐0+ Argentine hake Merluccius hubbsi Marini, 1933, one of the most important fishery resources in Argentina. The gulf exhibits strong seasonal and spatial fluctuations in environmental features, which might affect survival of age‐0+ individuals and recruitment to the adult population. Our main goal was to evaluate the seasonal and spatial dynamics of their nutritional status within the SJG in winter 2016, spring 2016 and summer 2017. Condition indices (relative condition factor Kn, hepatosomatic index HSI and liver lipid content %L) and diet information (feeding incidence and relative importance of prey) were combined with physical (temperature and salinity) and biological (satellite chlorophyll‐a concentration; chl‐a) data. Age‐0+ condition indices and prey intake showed significant seasonal variations, with minimum values in winter, intermediate in summer and maximum in spring, strongly coupled to the mean chl‐a concentration in each season. Herbivorous euphausiids Euphausia spp. were the preferred prey along the study period. A bottom‐up effect on condition of age‐0+ hake is suggested, manifested as lower condition values in winter, the less productive season. Spatially, better conditioned individuals matched sectors of the gulf where chl‐a concentrations were higher, coupled to the presence of frontal systems. Monitoring age‐0+ hake nutritional status is relevant in the current global change scenario, which might modify phytoplankton biomass and composition and, consequently, the herbivorous zooplankton abundances.Fil: Temperoni, Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Massa, Agueda Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Martos, Patricia. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Marinas; ArgentinaFil: Marrari, Marina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Characterization of the Western Antarctic Peninsula Ecosystem: Environmental Controls on the Zooplankton Community

The zooplankton community of Marguerite Bay, western Antarctic Peninsula, was investigated in relation to variability in chlorophyll concentrations and sea ice dynamics, using a combination of satellite remote sensing techniques and plankton net data. SeaWiFS chlorophyll data were validated with concurrent in situ data measured by HPLC and fluoromentric methods, and results indicate that SeaWiFS chlorophyll is an accurate measure of in situ values when HPLC data are used as ground truth. Climatology data of SeaWiFS chlorophyll west of the Antarctic Peninsula showed that the Bellingshausen Sea and Marguerite Bay usually had higher and more persistent chlorophyll concentrations compared with northern regions. These predictable phytoplankton blooms could provide the Antarctic krill, Euphausia superba, with the food required for successful reproduction and larval survival. Unusually high krill reproduction in 2000/2001 was coincident with above-average chlorophyll concentrations throughout the study area and was followed by the largest juvenile recruitment since 1981. High larval densities at the shelf break along the Antarctic Peninsula may have resulted, in part, from krill spawning in the Bellingshausen Sea. Interannual differences in sea ice also probably contributed to the variability in larval krill abundances. Interannual differences were observed in the species composition of the zooplankton of Marguerite Bay during fall, and these were linked to variability in the environmental conditions. Thysanoessa macrura was the most abundant euphausiid in 2001, while Euphausia crystallorophias dominated in 2002, and E. superba had intermediate densities during both years. Copepods were more abundant in 2001 by a factor of 2.6. Copepods and T. macrura showed a rapid population response to unusually high chlorophyll concentrations in the Bellingshausen Sea and Marguerite Bay during spring-summer 2000/2001, whereas E. superba and E. crystallorophias had a longer term response and showed increased recruitment in fall 2002. There were no clear associations between the distribution of zooplankton and environmental conditions in fall; however there was a significant relationship between chlorophyll concentrations in the Bellingshausen Sea during the preceding spring and zooplankton patterns during fall

Variability and 20-Year Trends in Satellite-Derived Surface Chlorophyll Concentrations in Large Marine Ecosystems around South and Western Central America

Marine ecosystems are under the increasing stress of natural and anthropogenic climate variability and change. Knowledge of the patterns of distribution of chlorophyll concentrations as an indicator of phytoplankton abundance, its spatial and temporal variability, and the processes that control this variability is required to better understand the dynamics of marine populations and their fluctuations, including species of ecological and commercial importance. The Patagonia (PLME), South Brazil (SBLME), Humboldt (HLME), and Pacific Coastal Central America (PCACLME) Large Marine Ecosystems (LMEs) around South and Western Central America support high primary productivity and fisheries catch. During the past few decades, climate change and warming in most ecosystems has become evident, which in combination with variations in production rates could impact the dynamics of marine ecosystems. The goal of this study is to assess the variability and longer-term trends in chlorophyll concentrations in the PLME, SBLME, HLME, and PCACLME, and to discuss implications for higher trophic levels. We use a combination of high-resolution satellite-derived chlorophyll concentration data from SeaWiFS (1997–2006) and MODIS Aqua (2002–2017) to examine spatial and temporal variability and analyze the record-length linear trends in these LMEs (25°N-60°S, 30–120°W). We use monthly composites with 2 × 2 km spatial resolution for the period of overlap between sensors (2002–2006) to compare retrievals and adjust the MODIS Aqua data series at all pixels using linear regressions. We then apply the corrections to the MODIS data and combine the SeaWiFS and adjusted MODIS datasets to generate the longest time series in chlorophyll concentrations to date in the region. Our results revealed significant increases in chlorophyll concentrations in large areas of the PLME (78.23%) and HLME (43.03%) during the last ~20 years, with large potential implications for trophic relationships and the reproductive success of fish. For the mostly subtropical SBLME (26.35%) and tropical PCACLME (13.35%), increasing trends were detected only in relatively small regions, while changes in the PLME and HLME are widespread. Results from this study contribute to a better understanding of the potential effects of environmental change on ecosystem dynamics and provide new tools to assess longer-term trends in satellite chlorophyll concentrations

Variability and 20-year trends in satellite-derived surface chlorophyll concentrations in large marine ecosystems around South and Western central America

Marine ecosystems are under the increasing stress of natural and anthropogenic climate variability and change. Knowledge of the patterns of distribution of chlorophyll concentrations as an indicator of phytoplankton abundance, its spatial and temporal variability, and the processes that control this variability is required to better understand the dynamics of marine populations and their fluctuations, including species of ecological and commercial importance. The Patagonia (PLME), South Brazil (SBLME), Humboldt (HLME), and Pacific Coastal Central America (PCACLME) Large Marine Ecosystems (LMEs) around South and Western Central America support high primary productivity and fisheries catch. During the past few decades, climate change and warming in most ecosystems has become evident, which in combination with variations in production rates could impact the dynamics of marine ecosystems. The goal of this study is to assess the variability and longer-term trends in chlorophyll concentrations in the PLME, SBLME, HLME, and PCACLME, and to discuss implications for higher trophic levels. We use a combination of high-resolution satellite-derived chlorophyll concentration data from SeaWiFS (1997-2006) and MODIS Aqua (2002-2017) to examine spatial and temporal variability and analyze the record-length linear trends in these LMEs (25°N-60°S, 30-120°W). We use monthly composites with 2 × 2 km spatial resolution for the period of overlap between sensors (2002-2006) to compare retrievals and adjust the MODIS Aqua data series at all pixels using linear regressions. We then apply the corrections to the MODIS data and combine the SeaWiFS and adjusted MODIS datasets to generate the longest time series in chlorophyll concentrations to date in the region. Our results revealed significant increases in chlorophyll concentrations in large areas of the PLME (78.23%) and HLME (43.03%) during the last ~20 years, with large potential implications for trophic relationships and the reproductive success of fish. For the mostly subtropical SBLME (26.35%) and tropical PCACLME (13.35%), increasing trends were detected only in relatively small regions, while changes in the PLME and HLME are widespread. Results from this study contribute to a better understanding of the potential effects of environmental change on ecosystem dynamics and provide new tools to assess longer-term trends in satellite chlorophyll concentrations.Fil: Marrari, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Universidad de Buenos Aires; ArgentinaFil: Piola, Alberto Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Universidad de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; ArgentinaFil: Valla, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval. Departamento Oceanografía; Argentina. Universidad de Buenos Aires; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentin

Spatial and Temporal Variability of SeaWiFS Chlorophyll \u3cem\u3ea\u3c/em\u3e Distributions West of the Antarctic Peninsula: Implications for Krill Production

SeaWiFS chlorophyll a distributions between 1997 and 2004 were investigated in relation to sea-ice dynamics for waters west of the Antarctic Peninsula (55–75°S, 50–80°W) in order to better understand the reproductive patterns and recruitment success of the Antarctic krill, Euphausia superba. Climatology patterns showed that the Bellingshausen Sea and Marguerite Bay region usually had higher chlorophyll a concentrations, which persisted throughout austral spring and summer, compared with more northern regions along the Antarctic Peninsula and the western Scotia Sea. These predictable and long-lasting phytoplankton accumulations could provide krill with the food levels required for successful reproduction and larval survival. Unusually high krill reproduction in 2000/2001 was coincident with above-average chlorophyll a concentrations throughout most of the study area and resulted in the largest juvenile recruitment (in 2001/2002) since 1981. High larval densities (up to 132 ind m−3) at the shelf break along the Antarctic Peninsula may have resulted, in part, from krill spawning in the Bellingshausen Sea. In general, ice-edge blooms were only a significant feature in the southern sectors of our study area, particularly in the Bellingshausen Sea and, thus, may not support krill reproduction in the northern Peninsula region as previously believed. Instead, phytoplankton blooms during spring in the northern region appeared to be governed by shelf-break processes, such as upwelling of iron-rich deep water. Interannual differences in sea ice also probably contributed to the variability in larval krill abundances observed in Marguerite Bay. Sea ice melted early in 2000/2001, allowing elevated phytoplankton blooms to develop. In contrast, sea ice persisted throughout spring and summer 2001/2002 limiting phytoplankton accumulation, particularly in southern Marguerite Bay. Thus, the early and extended availability of elevated chlorophyll a concentrations during spring and summer 2000/2001, particularly in the vicinity of Marguerite Bay and to the south in the Bellingshausen Sea, as well as reduced sea ice in coastal areas, likely supported the unusually high densities of larval krill observed during fall in waters west of the Antarctic Peninsula

Validation of SeaWiFS Chlorophyll \u3cem\u3ea\u3c/em\u3e Concentrations in the Southern Ocean: A Revisit

Surface chlorophyll a concentrations (Ca, mg m− 3) in the Southern Ocean estimated from SeaWiFS satellite data have been reported in the literature to be significantly lower than those measured from in situ water samples using fluorometric methods. However, we found that high-resolution (∼ 1 km2/pixel) daily SeaWiFS Ca (CaSWF) data (SeaDAS4.8, OC4v4 algorithm) was an accurate measure of in situ Ca during January–February of 1998–2002 if concurrent in situ data measured by HPLC (CaHPLC) instead of fluorometric (CaFluor) measurements were used as ground truth. Our analyses indicate that CaFluor is 2.48 ± 2.23 (n = 647) times greater than CaHPLC between 0.05 and 1.5 mg m− 3 and that the percentage overestimation of in situ Ca by fluorometric measurements increases with decreasing concentrations. The ratio of CaSWF/CaHPLC is 1.12 ± 0.91 (n = 96), whereas the ratio of CaSWF/CaFluor is 0.55 ± 0.63 (n = 307). Furthermore, there is no significant bias in CaSWF (12% and − 0.07 in linear and log-transformed Ca, respectively) when CaHPLC is used as ground truth instead of CaFluor. The high CaFluor/CaHPLC ratio may be attributed to the relatively low concentrations of chlorophyll b (Cb/Ca = 0.023 ± 0.034, n = 482) and relatively high concentrations of chlorophyll c (Cc/Ca = 0.25 ± 0.59, n = 482) in the phytoplankton pigment composition when compared to values from other regions. Because more than 90% of the waters in the study area, as well as in the entire Southern Ocean (south of 60° S), have CaSWF between 0.05 and 1.5 mg m− 3, we consider that the SeaWiFS performance of Ca retrieval is satisfactory and for this Ca range there is no need to further develop a “regional” bio-optical algorithm to account for the previous SeaWiFS “underestimation”

Spatial patterns of copepod biodiversity in relation to a tidal front system in the main spawning and nursery area of the Argentine hake Merluccius hubbsi

Copepods play an important role in marine ecosystems as a direct link of energy transfer between primary producers and higher trophic level consumers, such as fish. In the Argentine Sea, the Patagonian stock of Argentine hake Merluccius hubbsi spawns from late austral spring (December) to early autumn (April) in the northern Patagonian shelf region (43°?45°30′S), in association with a highly productive tidal front system. Since hake larvae prey mainly upon copepods, the objective of this study was to assess the spatial variability in the abundance and diversity of these potential food items in different sectors of the front, as one of the possible factors affecting hake recruitment success. Two complementary mesh sizes (67 and 300 μm) were used to accurately target the entire copepod size spectrum. The copepod community was dominated by developmental stages < 1 mm in total length (eggs, nauplii, copepodites of cyclopoids and calanoids), and adults of the species Oithona helgolandica, Microsetella norvegica, Ctenocalanus vanus and Drepanopus forcipatus. Their spatial distribution was highly influenced by the across-shelf characteristics of the tidal front system, highlighting the impact of environmental features, mainly bottom temperature and salinity, in shaping the community. Abundances were higher in the transitional relative to the stratified sector of the system. Such sector would provide the appropriate conditions to sustain M. hubbsi larval growth resulting from high availability of adequate prey, the suitable thermal ranges, and the existence of retention mechanisms.Fil: Temperoni, Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: Viñas, Maria Delia. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Martos, Patricia. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Marinas; ArgentinaFil: Marrari, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentin

Spatial patterns of mesozooplankton distribution in the Southwestern Atlantic Ocean (34(e41(S) during austral spring: relationship with the hydrographic conditions

The mesozooplankton community was analysed in a large region of the Argentine Shelf (34(e41(S) on the main spring spawning ground of the anchovy (Engraulis anchoita), and its spatial pattern was related to the hydrographic conditions. Copepods smaller than 1 mm dominated the community. Three faunistic areas were identified by cluster analysis: northern coastal area (NCA), southern coastal area (SCA), and shelf area (SA), each with distinct physical conditions. The NCA, influenced by the R ́ıo de la Plata estuary, had relatively high temperature, the lowest salinity, and the highest stratification values. The SCA had the highest salinity and a vertically homogeneous water column. The SA, vertically stratified, was influenced by the R ́ıo de la Plata estuary and by Subantarctic shelf waters and had the lowest temperature values and the greatest depths. Canonical correlation analysis was used to analyse the relationship between zooplankton and physical variables and four zooplankton assemblages were identified. Group A included the copepods Calanus australis, C. simillimus, Clausocalanus brevipes, Centropages brachiatus, Drepanopus forcipatus, Oithona atlantica, and O. helgolandica, and was preferentially distributed in the SA. Group B, composed of the copepods Acartia tonsa and Corycaeus spp. and the cladoceran Pleopis polyphemoides, showed a strong preference for the NCA. Group C included Labidocera fluviatilis, Ctenocalanus vanus, Paracalanus spp., Calanoides cf. carinatus, Euterpina acutifrons, Oithona nana, and the cladoceran Evadne nordmanni, and was preferentially distributed in coastal areas (NCA and SCA). Group D only included the cladoceran Podon intermedius and was mainly located in high salinity waters of the SCA. Small, omnivorous, fast-reproducing species ( groups B, D, and most of C) are better adapted to warmer variable and less productive coastal areas, whereas larger herbivorous species (most of group A) seem to better exploit colder stratified and more productive shelf waters. The mesozooplankton community provides adequate food for E. anchoita larvae in coastal areas and for adults in shelf waters.Fil: Marrari, Marina. University Of South Floridacollege Of Marine Science; . Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; ArgentinaFil: Viñas, Maria Delia. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; ArgentinaFil: Martos, Patricia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; ArgentinaFil: Hernandez, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Subsede Instituto Nacional de Investigación y Desarrollo Pesquero; Argentin