Photosynthetic efficiency and rapid light curves of sediment-biofilms along a water quality gradient in the Great Barrier Reef, Australia

Uthicke, Sven

doi:10.3354/meps322061

Cited by 26 publications

(31 citation statements)

References 40 publications

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“…We tested for interactive temperature and nitrate effects in a 28 d flow-through aquaria experiment mimicking inner (low light and high nutrient availability) and outer (high light and low nutrient availability) GBR inshore reef conditions (Uthicke 2006, Cooper et al 2007). Irrespective of nitrate and light availability, high (elevated by 2 to 3°C over current summer maxima) water temperatures of 31°C significantly reduced biofilm community 24 h net O 2 production and biomass (organic C, N and chl a contents).…”

Section: Discussionmentioning

confidence: 99%

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Interactive climate change and runoff effects alter O<sub>2 fluxes and bacterial community composition of coastal biofilms from the Great Barrier Reef

Witt¹,

Wild²,

Uthicke³

2012

Aquat. Microb. Ecol.

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Global (i.e. ocean warming) and local (i.e. land runoff) anthropogenic disturbances affect coastal coral reefs worldwide. Terrestrial runoff, leading to reduced light and increased nutrient availability, may have interactive effects with ocean warming in promoting shifts in benthic communities. Because microbial biofilms rapidly reflect environmental changes, we investigated the quantitative (C, N and chlorophyll a contents) and qualitative (microbial community composition) parameters and metabolic responses (O 2 fluxes) of biofilms established on glass slides to combinations of manipulated water temperatures (26, 29 and 31°C) ) in a 28 d flow-through aquarium experiment. The findings revealed that, independent of light availability, a temperature of 31°C significantly decreased the 24 h net O 2 production and all of the quantitative parameters. Under high light, additive effects of 31°C and 1.4 µM nitrate reduced the 24 h net O 2 production. Terminal restriction fragment length polymorphisms (T-RFLP) of 16S rRNA genes showed light-independent temperature-induced microbial community shifts driven by increases in the relative abundance of Oceanospirillum (Gammaproteobacteria) and decreases of Cyanobacteria. The relative abundances of diatom plastids increased in response to elevated nitrate only in high-lightexposed biofilms. Overall, high temperatures altered microbial biofilm community composition, biomass and productivity. Under predicted near-future inner reef scenarios (low light and high nitrate availability), biofilms become light-limited through sedimentation, while outer (high light and low nitrate availability) inshore reef biofilms remain nitrate-limited. Understanding the interactive effects of environmental changes on microbial biofilm communities may contribute to bioindicator development and improved coastal management strategies for coral reefs. Coral reefs harbour abundant microorganisms that predominantly exist as surface-attached communities (Costerton et al. 1995, Crump et al. 1998, Teske & Wooldridge 2001. Surface-colonising biofilms are complex communities comprising macromolecules and microorganisms embedded in an extracellular polymeric matrix (Mihm et al. 1981). These highly dynamic microbial biofilm communities respond rapidly to and are integrative of changing ambient environmental conditions (Paerl & Pinckney 1996, Snyder et al. 2005. Microbial biofilm communities also contribute significantly to biogeochemical nutrient cycling in aquatic ecosystems, such as coral reefs (Battin et al. 2003), and influence the settlement and metamorphosis of important reef building organisms, such as corals, therefore affecting the establishment, recovery and resilience of coral reefs (Wieczorek & Todd 1998, Webster et al. 2004). The immense surface area available for biofilm colonisation and development highlights the important contribution of biofilms to coral ecosystem functioning.Coral bleaching is promoted by increased SST (Hoegh-Guldberg 1999), and these effects may be exacerbated by ele...

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Section: Discussionmentioning

confidence: 99%

“…The analysis of the total chl a content was adapted for biofilms from protocols for freshwater phytoplankton and marine sediments (Sartory & Grobbelaar 1984, Uthicke 2006. Samples were kept in low light conditions and on ice during analysis.…”

Section: Spectrometric Determination Of Biofilm Chl a Contentmentioning

confidence: 99%

Interactive climate change and runoff effects alter O<sub>2 fluxes and bacterial community composition of coastal biofilms from the Great Barrier Reef

Witt¹,

Wild²,

Uthicke³

2012

Aquat. Microb. Ecol.

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“…Variation in foraminiferal taxa richness was mainly explained by an increase in the proportion of sediments with small grain sizes. While sediment grain size and inorganic carbon content are unlikely to be directly influenced by terrestrial runoff, the input, transformation, and retention of terrestrial nutrients, and suspended sediments can result in high organic sediment content and decreased light availability (Uthicke 2006;Cooper et al 2007).…”

Section: Foraminiferamentioning

confidence: 99%

“…Various other attributes of coral-reef communities, which could be considered indicators, change along water quality gradients of increasing turbidity and availability of nutrients and organic matter towards the GBR coast. For example, macroalgal cover increases, and abundance and richness of many hard-coral and octocoral taxa decrease (van Woesik et al 1999), maximum depth of reef development decreases (Cooper et al 2007), and benthic microalgae show physiological adaptations to low light levels (Uthicke 2006). Coral species richness is lower on GBR reefs adjacent to land with intense agriculture (DeVantier et al 2006), and octocorals shift from phototrophic to heterotrophic assemblages towards the coast (Fabricius and De'ath 2008).…”

Section: Introductionmentioning

confidence: 99%

Effectiveness of benthic foraminiferal and coral assemblages as water quality indicators on inshore reefs of the Great Barrier Reef, Australia

2009

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Although the debate about coral reef decline focuses on global disturbances (e.g., increasing temperatures and acidification), local stressors (nutrient runoff and overfishing) continue to affect reef health and resilience. The effectiveness of foraminiferal and hard-coral assemblages as indicators of changes in water quality was assessed on 27 inshore reefs along the Great Barrier Reef. Environmental variables (i.e., several water quality and sediment parameters) and the composition of both benthic foraminiferal and hard-coral assemblages differed significantly between four regions (Whitsunday, Burdekin, Fitzroy, and the Wet Tropics). Grain size and organic carbon and nitrogen content of sediments, and a composite water column parameter (based on turbidity and concentrations of particulate matter) explained a significant amount of variation in the data (tested by redundancy analyses) in both assemblages. Heterotrophic species of foraminifera were dominant in sediments with high organic content and in localities with low light availability, whereas symbiontbearing mixotrophic species were dominant elsewhere. A similar suite of parameters explained 89% of the variation in the FORAM index (a Caribbean coral reef health indicator) and 61% in foraminiferal species richness. Coral richness was not related to environmental setting. Coral assemblages varied in response to environmental variables, but were strongly shaped by acute disturbances (e.g., cyclones, Acanthaster planci outbreaks, and bleaching), thus different coral assemblages may be found at sites with the same environmental conditions. Disturbances also affect foraminiferal assemblages, but they appeared to recover more rapidly than corals. Foraminiferal assemblages are effective bioindicators of turbidity/light regimes and organic enrichment of sediments on coral reefs.

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“…Two ship-based cruises were conducted (wet season, February; dry season, August 2006). Sampling stations were along an intensively studied water quality gradient (Uthicke 2006, Cooper et al 2007, Uthicke and Nobes 2008, and the transects stretched from nearshore (e.g., Repulse Island, Long Island) to midshelf reefs (e.g., Hook and Bait reefs) with the influence of river runoff decreasing with distance from shore (see Fig. 1 in Cooper et al 2007).…”

Section: Methodsmentioning

confidence: 99%

Fluorescent lectin assay to quantify particulate marine polysaccharides on 96‐well filtration plates

Uthicke

Llewellyn

Eder

2009

Limnology & Ocean Methods

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Our aim was to develop a method to more broadly quantify particulate polysaccharides (PPs) to complement Alcian blue quantification of transparent exopolymer particles (TEPs), which are a subset of the ocean's pool of PPs. We used fluorescently labeled concanavalin A (FITC-conA), which is a lectin (a group of proteins that bind polysaccharides) and propose a method using 96-well filtration plate technology. ConA binds polysaccharides that contain the commonly occurring saccharides glucose and mannose. Using gum xanthan as a standard and field samples from the Great Barrier Reef (GBR), we demonstrated that marine particles (>0.4 µm) bound FITCconA in a concentration-dependent manner. Particulate polysaccharides measured by FITC-conA and Alcian blue (TEP only) in samples from 11 locations in the GBR were significantly correlated (R 2 = 0.61, P = 0.003). The lectin-based measurements were on average 80% higher, probably because Alcian blue stains acidic polysaccharides only, whereas lectins stain a broader polysaccharide spectrum. FITC-conA measurements of PPs in the wet season were on average 54% higher than in the dry season. PP concentrations correlated to concentrations of chlorophyll a, pheophytin, and particulate nitrogen, suggesting phytoplankton as an important source of PPs. Small volumes and few working steps enabled miniaturization of the FITC-conA protocol into a 96-well plate format, which provides for rapid sample throughput. In addition, there is extensive scope for further development using different lectins, naturally sourced standards, or filter size and capacity.

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Photosynthetic efficiency and rapid light curves of sediment-biofilms along a water quality gradient in the Great Barrier Reef, Australia

Cited by 26 publications

References 40 publications

Interactive climate change and runoff effects alter O<sub>2 fluxes and bacterial community composition of coastal biofilms from the Great Barrier Reef

Interactive climate change and runoff effects alter O<sub>2 fluxes and bacterial community composition of coastal biofilms from the Great Barrier Reef

Effectiveness of benthic foraminiferal and coral assemblages as water quality indicators on inshore reefs of the Great Barrier Reef, Australia

Fluorescent lectin assay to quantify particulate marine polysaccharides on 96‐well filtration plates

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