Impacts of ocean acidification in naturally variable coral reef flat ecosystems

Abstract Coral reefs are among the most sensitive ecosystems affected by ocean acidification and warming, and are predicted to shift from net accreting calcifier-dominated systems to net eroding algal-dominated systems over the coming decades. Here we present a long-term experimental study examining the responses of entire mesocosm coral reef communities to acidification (-0.2 pH units), warming (+ 2°C), and combined future ocean (-0.2 pH, + 2°C) treatments. We show that under future ocean conditions, net calcification rates declined yet remained positive, corals showed reduced abundance yet were not extirpated, and community composition shifted while species richness was maintained. Our results suggest that under Paris Climate Agreement targets, coral reefs could persist in an altered functional state rather than collapse.

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Assessing the impact of static and fluctuating ocean acidification on the behavior of Amphiprion percula

10.1101/2021.01.23.427511 ◽

2021 ◽

Author(s):

Matthew A. Vaughan ◽

Danielle L. Dixson

Keyword(s):

Coral Reef ◽

Ocean Acidification ◽

Reef Fishes ◽

Amphiprion Percula ◽

Behavioral Abnormalities ◽

Negative Impacts ◽

Ground Truthing ◽

Chemosensory Behavior ◽

The Impact

AbstractCoral reef organisms are exposed to both an increasing magnitude of pCO2, and natural fluctuations on a diel scale. For coral reef fishes, one of the most profound effects of ocean acidification is the impact on ecologically important behaviors. Previous behavioral research has primarily been conducted under static pCO2 conditions and have recently come under criticism. Recent studies have provided evidence that the negative impacts on behavior may be reduced under more environmentally realistic, fluctuating conditions. We investigated the impact of both present and future day, static (500 and 1000 μatm) and diel fluctuating (500 ± 200 and 1000 ± 200 μatm) pCO2 on the lateralization and chemosensory behavior of juvenile anemonefish, Amphiprion percula. Our static experimental comparisons support previous findings that under elevated pCO2, fish become un-lateralized and lose the ability to discriminate olfactory cues. Diel-fluctuating pCO2 may aid in mitigating the severity of some behavioral abnormalities such as the chemosensory response, where a preference for predator cues was significantly reduced under a future diel-fluctuating pCO2 regime. This research aids in ground truthing earlier findings and contributes to our growing knowledge of the role of fluctuating conditions.

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Pair formation, home range, and spatial variation in density, size and social status in blotched foxfaceSiganus unimaculatuson an Okinawan coral reef

PeerJ ◽

10.7717/peerj.1280 ◽

2015 ◽

Vol 3 ◽

pp. e1280 ◽

Cited By ~ 5

Author(s):

Atsushi Nanami

Keyword(s):

Coral Reef ◽

Home Range ◽

Spatial Variation ◽

Reef Flat ◽

Pair Formation ◽

Size Class ◽

Reef Slope ◽

Rocky Reef ◽

Seagrass Bed ◽

Agonistic Display

The present study examined pair formation, spatial pattern of home range and spatial variation in density, size and social status of blotched foxfaceSiganus unimaculatus(family Siganidae) on an Okinawan coral reef. Of 32 pairs sampled for sexing, 31 (96.9%) were heterosexual and showed size-assortative pairing. Developed ovaries were found in April and July, whereas oocytes were immature in August, September and February. Heterosexual pairing was found in both reproductive and non-reproductive periods. Home range size tended to be positively related to fork length (FL). The degree of home range overlap for same size class pairs was smaller than that for different size class pairs. The intraspecific behavior when two pairs approached each other was categorized as ‘attack,’ ‘agonistic display’ and ‘no interactions,’ and the frequency of agonistic behaviors (“attack” or “agonistic display”) was significantly greater than “no interactions.” Underwater observations at a seagrass bed, a rocky reef flat and a sheltered reef slope revealed that the mean FL was significantly smaller at the sheltered reef slope (4–13 cm) than at the rocky reef flat (>13 cm). No individuals were found in the seagrass bed. Most individuals less than 6 cm FL were solitary, whereas most individuals over 7 cm FL were paired. Density was significantly greater on the sheltered reef slope than on the rocky reef flat.

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Carbonate System Parameters of an Algal-dominated Reef along West Maui

10.5194/bg-2018-35 ◽

2018 ◽

Cited By ~ 1

Author(s):

Nancy G. Prouty ◽

Kimberly K. Yates ◽

Nathan Smiley ◽

Chris Gallagher ◽

Olivia Cheriton ◽

...

Keyword(s):

Coral Reef ◽

Reef Flat ◽

Sampling Period ◽

Total Alkalinity ◽

Carbonate Chemistry ◽

Diurnal Variability ◽

Carbon Chemistry ◽

Sources Of Pollution ◽

Seawater Ph ◽

Chemistry Dynamics

Abstract. Constraining coral reef metabolism and carbon chemistry dynamics are fundamental for understanding and predicting reef vulnerability to rising coastal CO2 concentrations and decreasing seawater pH. However, few studies exist along reefs occupying densely inhabited shorelines with known input from land-based sources of pollution. The shallow coral reefs off Kahekili, West Maui, are exposed to nutrient-enriched, low-pH submarine groundwater discharge (SGD) and are particularly vulnerable to the compounding stressors from land-based sources of pollution and lower seawater pH. To constrain the carbonate chemistry system, nutrients and carbonate chemistry were measured along the Kahekili reef flat every 4 h over a 6-d sampling period in March 2016. Abiotic process – primarily SGD fluxes – controlled the carbonate chemistry adjacent to the primary SGD vent site, with nutrient-laden freshwater decreasing pH levels and favoring undersaturated aragonite saturation (Ωarag) conditions. In contrast, diurnal variability in the carbonate chemistry at other sites along the reef flat was driven by reef community metabolism. Superimposed on the diurnal signal was a transition during the second sampling period to a surplus of total alkalinity (TA) and dissolved inorganic carbon (DIC) compared to ocean end-member TA and DIC measurements. A shift from net community production and calcification to net respiration and carbonate dissolution was identified. This transition occurred during a period of increased SGD-driven nutrient loading, lower wave height, and reduced current speeds. This detailed study of carbon chemistry dynamics highlights the need to incorporate local effects of nearshore oceanographic processes into predictions of coral reef vulnerability and resilience.

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