Cyanobacteria-dominated biofilms: a high quality food resource for intertidal grazers

Nagarkar, Sanjay; Williams, Gray A.; Gopalakrishnan, Subramaniam; Saha, Sukant

doi:10.1007/978-94-007-0944-7_12

Cited by 35 publications

(39 citation statements)

References 31 publications

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“…Such species are generally underappreciated in terms of ecosystem functioning, which is likely disproportionate to their biomass (Bracken and Low 2012). Their high turnover and palatability (with some exceptions) contribute to food web support (Nicotri 1977, Underwood 1984, Nagarkar et al 2004, and cyanobacteria might be important in fixing nitrogen on rocky shores (Stewart 1967, Magalha¨es et al 2005. Under conditions of increased physical stress, such taxa will become relatively more important in the community, with largely unstudied consequences for ecosystem functioning.…”

Section: Discussionmentioning

confidence: 99%

Additive effects of physical stress and herbivores on intertidal seaweed biodiversity

Williams

Jones

2013

Ecology

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Abstract. Patterns in rocky intertidal seaweed biodiversity influence the resilience and functioning of these important primary producer communities. In turn, seaweed biodiversity patterns are the result of many ecological factors. We determined the influences of thermal and desiccation stress, herbivory, and nutrients on seaweed biodiversity on a northern California rocky shoreline. In a fully crossed design at two tidal heights at wave-protected and exposed sites, we deployed screens to reduce stress, removed herbivores, and added nutrients for 18 months. The treatments reduced temperature, increased relative humidity, decreased herbivore abundances, and increased nitrogen in both seawater and seaweeds. Seaweed abundance and biodiversity (cover, biomass, species richness, diversity, evenness, and community composition) were influenced by tidal height, physical stress, and herbivores. Wave exposure affected all response variables except biomass and evenness. Stress and herbivores had independent additive effects on seaweed abundance and diversity. Physical stress did not make the community as a whole more susceptible to herbivores, and screens had overarching positive effects on seaweed biodiversity even though they also had positive effects on herbivore abundance. Nutrients had virtually no effect on seaweed biodiversity, and we observed no bottom-up effects of nutrient addition on herbivore density or biomass. Small green algae and diatoms were important contributors to overall algal cover and to changes in composition across treatments, but larger macroalgae dominated the species richness response. The striking absence of interactions between stress and herbivory highlights how seaweed communities can respond independently to important drivers of biodiversity. Thus, nonadditive, potentially synergistic effects do not necessarily complicate the understanding of how seaweed biodiversity responds to environmental change.

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Section: Discussionmentioning

confidence: 99%

Additive effects of physical stress and herbivores on intertidal seaweed biodiversity

Williams

Jones

2013

Ecology

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“…Increased amounts of green micro-algae on concrete may, at least in part, be due to increased numbers of sporelings of the ephemeral macro-algae that developed on this substratum. Although cyanobacteria may have limited value as food for grazers, Nagarkar et al (2004) found that epilithic cyanobacteria can be superior as food over other micro-algae, in terms of their protein, calorific content and, sometimes, carbohydrates. Thus, increased amounts of microalgae, plus their composition, may have explained greater survival of each species on concrete.…”

Section: Discussionmentioning

confidence: 99%

Differential patterns of distribution of limpets on intertidal seawalls: experimental investigation of the roles of recruitment, survival and competition

Iveša¹,

Chapman²,

Underwood³

et al. 2010

Mar. Ecol. Prog. Ser.

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On artificial surfaces (seawalls) in Sydney Harbour (Australia), local biodiversity of grazers differs between sandstone and concrete constructions because limpets Siphonaria denticulata are more abundant on sandstone, while Patelloida latistrigata are more abundant on concrete walls. Competition between siphonarian and patellid limpets is unstudied on artificial structures, although the limpets are common and are known to compete in natural habitats. We tested hypotheses that the substratum (concrete or sandstone), intra-and/or interspecific competition, or a combination of factors, influence recruitment, survival, rates of grazing, or the quantity and types of algal food to explain the observed patterns. Such analyses enable better understanding of the processes influencing diversity. Both species recruited more to concrete than to sandstone plates. S. denticulata recruited more in the presence of conspecifics and slightly less in the presence of P. latistrigata. Results varied between locations and experiments, but each species survived better on concrete, which had more macro-and micro-algal food. Increased densities of P. latistrigata reduced survival of conspecifics and of S. denticulata. S. denticulata had no effect on survival of P. latistrigata, but reduced amounts of macro-algae. P. latistrigata did not affect macro-algae. Initially, there were more micro-algae on concrete and a minor effect of large densities of S. denticulata. After 95 d, differences between habitats decreased and P. latistrigata were more strongly associated with reduced amounts of micro-algae. Neither substratum, density, nor mix of limpets affected rates of grazing. Thus, interspecific interactions were similar to predictions from knowledge of natural habitats, despite the different characteristics of artificial habitats and the reduced intertidal area available for grazing. Recruitment and competition were important in explaining different densities of these limpets on sandstone and concrete walls. Increasing urbanization requires more experimental tests to identify how well current theories of intertidal ecology and of the processes maintaining local biodiversity can apply to artificial shorelines.

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“…Little information is available about cyanobacterial interactions with herbivores in microbial mats. In spite of a high nutritional quality in terms of protein, carbohydrate and caloric value (Nagarkar et al, 2004), the cyanobacteria seem to be a low-preference food item for many marine herbivores because of the presence of secondary metabolites which effectively deter feeding (Hoffmann, 1999). However, some reports mention that mats are heavily grazed by holothurians (Sournia, 1976), whereas some mesograzers such as the gastropods Stylocheilus striatus, Haminoea cymbalum and H. ovalis feed exclusively on cyanobacteria (Cruz-Rivera & Paul, 2007).…”

Section: Factors Influencing Cyanobacterial Abundance and Nitrogenasementioning

confidence: 99%

Factors influencing microbial mat composition, distribution and dinitrogen fixation in three western Indian Ocean coral reefs

Charpy

Palińska

Abed

et al. 2012

European Journal of Phycology

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Cyanobacteria have been found to be important for primary production and nitrogen supply on coral reefs. Here, the distribution of cyanobacteria that dominate microbial mats (identified by using microscopic and molecular tools), their abundance, and specific contributions and timing of N 2 fixation, were studied in two coral reef systems of the western Indian Ocean: Mayotte (Comoros) and Tulear (Toliara, Madagascar). The results were compared with previously published data from the reefs of La Re´union Island (Mascarenes). Variations in nutrient levels, temperature and light penetration (Secchi) were also measured and compared. The reefs in Mayotte are situated in oligotrophic ocean waters and support coral reefs in good condition. The reef of Tulear was overgrown by algae. The shallow lagoon and reef in La Re´union showed signs of eutrophication and coral degradation. All three reefs maintained a diverse population of benthic cyanobacterial mats. A total of 13 different cyanobacterial morphotypes were encountered, belonging mainly to the genera Anabaena, Hydrocoleum, Leptolyngbya and Lyngbya (as identified by morphotypes and 16 S RNA analyses), but with variable abundances. Twelve of the 13 dominant cyanobacteria observed in the three sites fixed dinitrogen with daily rates of up to 42 nmol N 2 mg À1 Chl a.Maximum values were achieved by the heterocystous Anabaena sp. during daylight in Mayotte, which exhibited strongly lightstimulated nitrogenase activity. Mats dominated by non-heterocystous cyanobacteria fixed both during daylight and the night, with daily rates up to 38 nmol N 2 mg À1 Chl a (by Lyngbya majuscula, Mayotte). Hydrocoleum-dominated mats fixed N 2 at rates between 0 (H. glutinosum, Tulear) and 23.4 nmol N 2 mg À1 Chl a (H. coccineum, Mayotte). Cyanobacteria are normal constituents of the benthic microflora in tropical regions, but their abundance, diversity and species composition changes with environmental conditions and so do the rates of N 2 fixation on the lagoon floors.

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Cyanobacteria-dominated biofilms: a high quality food resource for intertidal grazers

Cited by 35 publications

References 31 publications

Additive effects of physical stress and herbivores on intertidal seaweed biodiversity

Additive effects of physical stress and herbivores on intertidal seaweed biodiversity

Differential patterns of distribution of limpets on intertidal seawalls: experimental investigation of the roles of recruitment, survival and competition

Factors influencing microbial mat composition, distribution and dinitrogen fixation in three western Indian Ocean coral reefs

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