RESUMO
In the absence of instrumental records, shell growth increments of bivalves are used to build continuous multi-decadal time series of growth and to estimate environmental variability. While there is interest in such chronologies in the Northern Hemisphere, there is a lack of multi-decadal datasets of growth for marine species from the Southern Hemisphere. We assessed the potential of the clam Glycymeris longior as an environmental proxy archive for the mid-latitudes of the South Atlantic Ocean, by applying sclerochronological techniques on the shells of individuals from a coastal area in Northern Patagonia, Argentina. Growth of G. longior showed a synchronous pattern, and shells were cross dated. We demonstrated that G. longior shells can be used to generate a robust multi-decadal chronology. The chronology spanned for a period of 22 years, from 1990 to 2011. This chronology has the potential to be extended, given that the maximum longevity of the analysed shells was 69 years. Significant positive correlations were found between the chronology and sea surface temperature and the Southern Annular Mode index. The sclerochronological approach performed in this study is a first step toward a long-term understanding of the links between climate and growth patterns of bivalves in temperate regions of SW Atlantic Ocean, under a long-term perspective.
Assuntos
Bivalves/crescimento & desenvolvimento , Clima , Monitoramento Ambiental , Animais , Argentina , Oceano AtlânticoRESUMO
The Gulf of Mexico (GoM) is home to the world's largest remaining wild oyster fisheries, but baseline surveys needed to assess habitat condition are recent and may represent an already-shifted reference state. Here, we use prehistoric oysters from archaeological middens to show that oyster size, an indicator of habitat function and population resilience, declined prior to the earliest assessments of reef condition in an area of the GoM previously considered pristine. Stable isotope sclerochronlogy reveals extirpation of colossal oysters occurred through truncated life history and slowed growth. More broadly, our study suggests that management strategies affected by shifting baselines may overestimate resilience and perpetuate practices that risk irreversible decline.
Assuntos
Crassostrea , Animais , Ecossistema , Pesqueiros , Golfo do México , MéxicoRESUMO
Historical coral growth assessed by sclerochronology records provides an environmental retrospective and future perspective on the maintenance of coral-reef ecosystems. Three growth parameters, extension rate, skeletal density, and calcification rate were evaluated over the past two decade's interval (1988-2013) in different gender of two massive corals Pavona gigantea and Porites panamensis. The species P. gigantea calcified two-times faster (0.84 ± 0.29 g cm-2 yr-1) than P. panamensis (0.36 ± 0.15 g cm-2 yr-1); and male colonies presents13-58% higher calcification rates than females. Annual growth parameters do not show significant trends over the period 1988-2013, but significant, growth disruption associated with ENSO events. The data presented here suggest that P.gigantea and P.panamensis from the area have developed phenotypic plasticity to a wide range of environmental condition; the life history of both species is reflected in their calcification rates during both optimal and non-optimal conditions over the last two decades. Massive species develop denser structures that provide a permanent habitat to many marine species and contributes to the long-term maintenance of coral reef communities in the eastern tropical Pacific.
Assuntos
Antozoários/crescimento & desenvolvimento , Recifes de Corais , Monitoramento Ambiental , AnimaisRESUMO
The rough scad, Trachurus lathami Nichols, 1920, is a small pelagic species distributed along the West Atlantic coast. It is most abundant in the Southern Brazil (28°30-34°S) and in the Southeastern Brazilian Bight (SEBB, 22°-28°30S). The rough scad is fished by purse seines, which main target is the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879). Age and growth are vital to understand the life cycle of a species, to fishery management and ecosystem modeling. This study aimed to assess the age and growth of T. lathami, to identify its age structure in the SEBB, and to evaluate what causes the wide differences among Trachurus species in terms of body size and growth parameters. Data available on T. lathami was attained between 2008 and 2010 from surveys at SEBB. A total of 278 whole otoliths of T. lathami, total length between 27 mm and 208 mm, were analyzed and compared with the only other source of otolith data, from 1975. Three blind readings were performed and assessed using traditional methods to study fish age and growth. Zero up to eight rings were found, each ring corresponding to one year in the life of an individual of this species. The von Bertalanffy growth model parameters were L∞ = 211.90 mm and K = 0.319 year-1. The results of the analyses have shown similarities between 1975 and 2008-2010, indicating that the otolith development, the growth pattern and the age structure remained stable. T. lathami is the smallest species of Trachurus and it has the highest growth rates among them. This is probably related to the different temperatures where larvae/juvenile and adult grow, to the absence of a strong fishing pressure and to decadal population variability.(AU)
Assuntos
Animais , Perciformes/crescimento & desenvolvimento , Distribuição por Idade , Oceano Atlântico , Costa , BrasilRESUMO
The rough scad, Trachurus lathami Nichols, 1920, is a small pelagic species distributed along the West Atlantic coast. It is most abundant in the Southern Brazil (28°30-34°S) and in the Southeastern Brazilian Bight (SEBB, 22°-28°30S). The rough scad is fished by purse seines, which main target is the Brazilian sardine, Sardinella brasiliensis (Steindachner, 1879). Age and growth are vital to understand the life cycle of a species, to fishery management and ecosystem modeling. This study aimed to assess the age and growth of T. lathami, to identify its age structure in the SEBB, and to evaluate what causes the wide differences among Trachurus species in terms of body size and growth parameters. Data available on T. lathami was attained between 2008 and 2010 from surveys at SEBB. A total of 278 whole otoliths of T. lathami, total length between 27 mm and 208 mm, were analyzed and compared with the only other source of otolith data, from 1975. Three blind readings were performed and assessed using traditional methods to study fish age and growth. Zero up to eight rings were found, each ring corresponding to one year in the life of an individual of this species. The von Bertalanffy growth model parameters were L∞ = 211.90 mm and K = 0.319 year-1. The results of the analyses have shown similarities between 1975 and 2008-2010, indicating that the otolith development, the growth pattern and the age structure remained stable. T. lathami is the smallest species of Trachurus and it has the highest growth rates among them. This is probably related to the different temperatures where larvae/juvenile and adult grow, to the absence of a strong fishing pressure and to decadal population variability.