Decadal losses of canopy-forming algae along the warm temperate coastline of Brazil

Author(s):Show less -

Gorman, Daniel ^[1] ; Horta, Paulo ^[2] ; Flores, Augusto A. V. ^[1] ; Turra, Alexander ^[3] ; de Souza Berchez, Flavio Augusto ^[4] ; Batista, Manuela B. ^[2] ; Lopes Filho, Euro S. ^[5] ; Melo, Mariana S. ^[4] ; Ignacio, Barbara L. ^[6] ; Carneiro, Ivan M. ^[7] ; Villaca, Roberto C. ^[8] ; Szechy, Maria Teresa M. ^[7]

Affiliation

^[1] Univ Sao Paulo, Ctr Marine Biol, Sao Sebastiao - Brazil

^[2] Univ Fed Santa Catarina, Ctr Ciencias Biol, Dept Bot, Lab Ficol, Florianopolis, SC - Brazil

^[3] Univ Sao Paulo, Inst Oceanog, Sao Paulo - Brazil

^[4] Univ Sao Paulo, Inst Biociencias, Sao Paulo - Brazil

^[5] eQuanta, Sao Paulo - Brazil

^[6] Univ Fed Sao Paulo, Santos, SP - Brazil

^[7] Univ Fed Rio de Janeiro, Inst Biol, Dept Bot, Rio De Janeiro - Brazil

^[8] Univ Fed Fluminense, Inst Biol, Niteroi, RJ - Brazil

• Document type: Journal article
• Source: GLOBAL CHANGE BIOLOGY; v. 26, n. 3 JAN 2020.
• Web of Science Citations: 0

Abstract

The loss of canopy-forming seaweeds from urbanized coasts has intensified in response to warming seas and non-climatic pressures such as population growth and declining water quality. Surprisingly, there has been little information on the extent of historical losses in the South-western Atlantic, which limits our ability to place this large marine ecosystem in a global context. Here, we use meta-analysis to examine long-term (1969-2017) changes to the cover and biomass of Sargassum spp. and structurally simple algal turfs along more than 1,000 kilometres of Brazil's warm temperate coastline. Analysis revealed major declines in canopy cover that were independent of season (i.e., displaying similar trends for both summer and winter) but varied with coastal environmental setting, whereby sheltered bays experienced greater losses than coastal locations. On average, covers of Sargassum spp. declined by 2.6% per year, to show overall losses of 52% since records began (ranging from 20% to 89%). This contrasted with increases in the cover of filamentous turfs (24% over the last 27 years) which are known to proliferate along human-impacted coasts. To test the relative influence of climatic versus non-climatic factors as drivers of this apparent canopy-to-turf shift, we examined how well regional warming trends (decadal changes to sea surface temperature) and local proxies of coastal urbanization (population density, thermal pollution, turbidity and nutrient inputs) were able to predict the changes in seaweed communities. Our results revealed that the most pronounced canopy losses over the past 50 years were at sites exhibiting the greatest degree of coastal warming, the highest population growth and those located in semi-enclosed sheltered bays. These findings contribute knowledge on the drivers of canopy loss in the South-western Atlantic and join with global efforts to understand and mitigate declines of marine keystone species. (AU)

• FAPESP's process: 18/06162-6 - Evaluation of the current and future potential for marine protected areas (MPa) to safeguard the biodiversity, function and resilience of subtidal rocky seascapes in subtropical Brazil
• Grantee: Daniel Gorman
• Support type: Scholarships in Brazil - Young Researchers
• FAPESP's process: 16/26064-3 - Evaluation of the current and future potential for Marine Protected Areas (MPa) to safeguard the biodiversity, function and resilience of subtidal rocky seascapes in subtropical Brazil
• Grantee: Daniel Gorman
• Support type: Research Grants - Young Investigators Grants