Marcia A.O. Figueiredo a,b,c, Ingvar Eide d,*, Marcia Reynier e, Alexandre B. Villas-Bôas a,c, Frederico T.S. Tâmega b,c, Carlos Gustavo Ferreira c, Ingunn Nilssen d,f, Ricardo Coutinho c, Ståle Johnsen d
a Instituto de Pesquisa Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão 915, Jardim Botânico 22460-030, Rio de Janeiro, RJ, Brazil
b Instituto Biodiversidade Marinha, Avenida Ayrton Senna 250, Sala 208, Barra da Tijuca, 22793-000, Rio de Janeiro, RJ, Brazil
c Instituto de Estudos do Mar Almirante Paulo Moreira, Departamento de Oceanografia, Divisão de Biotecnologia Marinha, Rua Kioto 253, 28930-000, Arraial do Cabo, RJ, Brazil d Statoil ASA, Research, Development and Innovation, N-7005 Trondheim, Norway
e LABTOX – Laboratório de Análise Ambiental Ltda., Avenida Carlos Chagas Filho, 791, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ 21941-904, Brazil f
Trondhjem Biological Station, Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway
Article history:
Received 4 February 2015
Revised 17 April 2015
Accepted 18 April 2015
Available online xxxx
Keywords: Environmental impact, Sediment load, Photosynthesis, Correlation analysis, Calcareous algae, Multivariate data analysis
Abstract
The impact of sediment coverage on two rhodolith-forming calcareous algae species collected at 100 m water depth off the coast of Brazil was studied in an experimental flow-through system. Natural sediment mimicking drill cuttings with respect to size distribution was used. Sediment coverage and photosynthetic efficiency (maximum quantum yield of charge separation in photosystem II, /PSIImax) were measured as functions of light intensity, flow rate and added amount of sediment once a week for nine weeks. Statistical experimental design and multivariate data analysis provided statistically significant regression models which subsequently were used to establish exposure–response relationship for photosynthetic efficiency as function of sediment coverage. For example, at 70% sediment coverage the photosynthetic efficiency was reduced 50% after 1–2 weeks of exposure, most likely due to reduced gas exchange. The exposure–response relationship can be used to establish threshold levels and impact categories for environmental monitoring.
1. Introduction
Rhodolith beds are benthic communities dominated by calcareous red algae (Rhodophyta: Corallinales and Sporolithales) which
build calcified nodules (rhodoliths) (Bosence, 1983; Foster, 2001). Rhodoliths with multi spherical structures are classified within the morphological group ‘‘boxwork’’ (Basso, 1998). Due to the structure, the rhodoliths are inhabited by other organisms increasing the biodiversity of soft-bottom communities (Bordehore et al., 2003; Steller et al., 2003; Figueiredo et al., 2007; Harvey and Bird, 2008; Sciberras et al., 2009) and therefore they play an important ecological role in coastal areas (Hall-Spencer, 1998; Ávila and Riosmena-Rodriguez, 2009; Steller et al., 2009; Riosmena-Rodriguez et al., 2010).
The largest occurrence of rhodolith beds in the world are found in the southwest Atlantic along most of the Brazilian continental shelf (Kempf, 1970; Foster, 2001; Lavrado, 2006; Amado Filho et al., 2012). Calcareous algae are found down to approximately 250 m depth (Littler et al., 1986, 1991). These communities may be disturbed and have a potential to get buried due to natural sedimentation and anthropogenic activities such as fishtrawling and mining (Nelson, 2009). Rhodolith beds are increasingly exposed to discharges of drill cuttings from oil and gas activities, for instance in the Gulf of Mexico and on the Brazilian shelf (Davies et al., 2007). It has been demonstrated that fine sediments (<250 lm grain size) may reduce the photosynthetic activity of coralline algae to a larger extent than coarse calcareous sediments from shallow nutrient-rich estuarine and coastal environment (Wilson et al., 2004; Harrington et al., 2005; Riul et al., 2008) as well as deep rhodolith soft-bottoms (Villas-Bôas et al., 2014). The ability to withstand sedimentation varies greatly among calcareous algae species (Harrington et al., 2005; Villas-Bôas et al., 2014). Different species may have different survival strategy towards sedimentation, for example slow growth and low metabolic demand, shooting branches above thallus surface, translocation of photosynthesis through cell-fusions from healthy to damaged area of thallus, or tilting (Steneck, 1986; Dethier and Steneck, 2001). […]