Banca de DEFESA: ANA CAROLINA GRILLO MONTEIRO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : ANA CAROLINA GRILLO MONTEIRO
DATE: 27/03/2025
TIME: 08:30
LOCAL: DECOL/CB/UFRN (Sala de reuniões)
TITLE:

Benthic competition on coral reefs: outcomes, mechanisms, and effects of environmental stressors

KEY WORDS:

Coral reef; Scleractinia; hard coral; macroalga; zoantharian;soft coral; ecological interaction; eutrophication; climate change; acidification

PAGES: 147
BIG AREA: Ciências Biológicas
AREA: Ecologia
SUMMARY:

Competition among organisms is one of the strongest ecological interactions structuring terrestrial and aquatic communities. In reef ecosystems, sessile organisms compete for the limited hard substrate available to settle and grow, and they use a range of mechanisms to maintain their space and outcompete organisms nearby. Hard corals are one of the main calcifying organisms that build reefs, and current anthropogenic disturbances are declining their abundance and shifting the benthic dominance on reefs to soft-bodied taxa like macroalgae, zoantharians, and soft corals, that can outcompete hard corals for substrate. However, the effects of competitive interactions can vary according to the organisms involved and the environmental factors that influence their competitive ability. This thesis aimed to investigate the outcomes of competition between hard corals and macroalgae, soft corals, and zoantharians from Southwestern Atlantic and Indo-Pacific reefs, the mechanisms of competition, and how environmental stressors affect the outcome of these interactions, through a combination of laboratory experiments.In the first two chapters I investigated the mechanisms and outcomes of competition involving hard corals from the Southwest Atlantic (Siderastrea sp. and Millepora alcicornis) and the Indo-Pacific (Porites sp. and Acropora sp.), competing with common local competitors: a macroalga (Dictyopteris delicatula) and a zoantharian (Palythoa caribaeorum) in the first case, and a soft coral (Clavularia sp.) in the second. In Chapter 1, both competitors only harmed the hard corals upon physical contact, with the zoantharian being a stronger competitor than the macroalga. In Chapter 2, the soft coral negatively affected the weakest hard coral through mechanical damage, but its allelochemicals did not impact any hard coral. Both chapters demonstrated that the susceptibility to damage from competition in hard corals depends on the species: M. alcicornis suffered more damage than Siderastrea sp. when competing with the macroalga but both corals were highly affected when contacted by the zoantharian, and Acropora sp. did not suffer damage by the soft coral while Porites sp. was negatively affected. In Chapter 3, I assessed the effects of iron enrichment on physical competition between three hard corals (Siderastrea sp., M. alcicornis, and Mussismilia harttii) and a macroalga (Lobophora variegata) and a zoantharian (P. caribaeorum), considering the potential effects of mining dam rupture disasters that occurred on the Brazilian coast. Competition was deleterious for all hard corals irrespective of iron, but high iron enrichment aggravated the negative impacts of competition on the most vulnerable coral, M. harttii.Finally, in Chapter 4, I investigated separate and combined effects of nitrate enrichment and acidification on competition between a hard coral (Stylophora pistillata) and soft coral (Xenia sp.) from the Indo-Pacific. While competition negatively affected the hard coral, the combination of ocean acidification and nitrate enrichment mitigated the negative effects on itsendosymbionts, but acidification reduced its calcification rates. The physiological parameters of the soft coral were favored by nitrate enrichment and ocean acidification had no impacts. Overall, hard corals suffered detrimental effects in physical contact interactions with the competitors, and most of the organisms interacting with the hard corals did not exhibit detectable damage from competition. This thesis demonstrates that: the severity of competition effects on hard corals and the mechanisms used by competitors depend on the species involved, environmental stressors related to pollution present more risks to hard corals when they are competing with other benthic organisms, and scenarios with increasing anthropogenic stressors, either related to climate (global scale) or pollution (local scale), tend to favor soft-bodied competitors. These results add more information to better comprehend the specificities of competitive interactions on benthic reef ecosystems and enablemore accurate forecasts of the consequences of increasing anthropogenic stressors and dominance of competitively superior organisms in reef ecosystems.

COMMITTEE MEMBERS:
Presidente - 2319234 - GUILHERME ORTIGARA LONGO
Externo à Instituição - IGOR CRISTINO SILVA CRUZ - UFBA
Externa à Instituição - BÁRBARA SEGAL RAMOS - UFSC
Externo à Instituição - RALF TARCISO SILVA CORDEIRO - UFRPE
Externo à Instituição - SAMUEL COELHO DE FARIA - USP