How does rising atmospheric CO2 affect marine organisms?

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Braganša Peninsula, Eastern Amazon Region, Brazil
Cohen, M.C.L., Behling, H. and Lara, R.J. 2005. Amazonian mangrove dynamics during the last millennium: The relative sea-level and the Little Ice Age. Review of Palaeobotany and Palynology 136: 93-108.

Cohen et al. (2005) used stratigraphy, pollen analysis and radiocarbon dating to reconstruct the environmental history of the Braganša Peninsula (0.88░S, 46.67░W) over the past 1000 years, focusing on vegetation development in the central part of the peninsula, where boundaries of mangrove and salt marshes occur, and where sensitive vegetation changes related to relative sea-level changes could be expected. Their results indicated a broad period between AD 1150 and the late 1800s characterized by low inundation frequency (lower sea levels), with the exception of a brief interval of higher sea levels during the Little Medieval Warm Period. Higher sea levels were also observed from the start of the record until around 1130 and during the 20th century. With regard to the cause of these fluctuations, the authors note that the data "strongly point" to global climatic changes that have occurred during the last 1000 years, specifically mentioning the Little Ice Age. Of the present mangrove migration, they further note that it is likely associated "with the global tendency of an eustatic sea-level rise, due to the increase in temperature and glaciers melting around the world during the last 150 years." Given this interpretation and their additional statement that "for the period between 1000 and 1150 AD, relative sea-level was similar to the current sea-level," we can infer that temperatures during this latter stage of the Medieval Warm Period were likely similar to temperatures of the Current Warm Period.