Long term marine time-series expose underlying climate-driven changes in South America during the last 40 years

ARIAS, ANDRÉS HUGO; ALBERDI, ERNESTO; FREIJE, R.H.; JORGE E. MARCOVECCHIO

Paris

Conferencia; Our common future under climate change, International Scientific Conference; 2015

IRD, CNRS, French Government, UNESCO, etc.

Climate Change is creating a dynamic of continuous changes in ecosystems. Generally, the expected consequences of these changes are global; however, the occurrence of extreme events and specific environmental problems are usually local or regional phenomenon. One of the keys to uncover climate-driven changes are the long term time-series of observations. While there are a number of long-term biological time-series on land, there are relatively few in marine environments. This is highlighted by the fact that the Intergovernmental Panel on Climate Change (IPCC) noted 28586 significant biological changes in terrestrial systems, but only 85 from marine and freshwater systems. The present research deals with this gap in the state of the art, focusing in an area which holds scarce to null long-term research on ocean observation and climate driven changes: the South Atlantic Ocean. From the results of the analysis of up to 40 years of oceanographic physicochemical variables measured at the Bahia Blanca Estuary (Dissolved Oxygen, pH, Chlorophyll, Phaeopigments, Temperature, Salinity, NH4, Particulate Organic Matter, NO2, NO3, Phosphorous, etc.) unknown underlying trends were uncovered. In order to test the variables trend throughout several time-scales, the continuous wavelet transform (CWT) was used to divide the continuous-time function into wavelets. Moreover, the use of Cross Wavelet Correlation (CWC) allowed to light the relationship between the variables throughout different time-scales. After that, a correlation analysis which linked the ocean observations to biological documented changes was assessed. As result, novel hypotheses were raised in the field of phytoplankton and zooplankton assemblages climate-driven control, crustaceans catches and fisheries recruitment. For instance, ?climate-driven variations in ocean Temperature, pH, DO and Salinity can restrict the growth of the phytoplankton assemblages, leading to other factors (i.e., grazing) the size control of the cells? and ?low interannual variability of water temperature and water salinity favours higher fishing yields and vice versa?. Undoubtedly, these findings will strengthen the theory which propose climate-driven changes at marine coastal ecosystems as a consequence of global climate change and will be of high relevance for the international dialogue on ?anthropogenic vs. climate-induced changes? over the oceanic ecosystems.