Variability of the carbonate chemistry in a shallow, seagrass-dominated ecosystem: implications for ocean acidification experiments

Challener, Roberta C.; Robbins, Lisa L.; McClintock, James B.

doi:10.1071/mf14219

Cited by 55 publications

(44 citation statements)

References 43 publications

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“…The pH range recorded in Little Cayman seagrass beds (0.51-0.62 pH units) is therefore consistent with previous reports, and is similar to the pH range reported from a study of Grape Tree Bay in 2011 (0.47 pH units, Barry et al, 2013). These substantial fluctuations in pH result from changes in pCO 2 driven by seagrass photosynthesis and respiration (Semesi et al, 2009;Saderne et al, 2013;Challener et al, 2016). Covariance of DO with pH is also consistent with previous reports (Barry et al, 2013), and supports the idea that seawater chemistry is altered by seagrasses (Challener et al, 2016).…”

Section: Physicochemical Conditionssupporting

confidence: 79%

“…These substantial fluctuations in pH result from changes in pCO 2 driven by seagrass photosynthesis and respiration (Semesi et al, 2009;Saderne et al, 2013;Challener et al, 2016). Covariance of DO with pH is also consistent with previous reports (Barry et al, 2013), and supports the idea that seawater chemistry is altered by seagrasses (Challener et al, 2016). Although physicochemical conditions fluctuated less on the back-reef, variability was still high compared to the open ocean reference site.…”

Section: Physicochemical Conditionssupporting

confidence: 77%

“…High physicochemical variability has also been reported for shallow seagrass beds globally; a diel temperature range of as much as 6 • C has been reported for shallow seagrass beds (Semesi et al, 2009), consistent with the range of up to 6.7 • C recorded in the present study. Similarly, mean diel fluctuations of 0.34 (Saderne et al, 2013) to 0.35 pH units (Challener et al, 2016) have been reported previously from studies of macrophyte beds. One study reported diel fluctuations in excess of 1 pH unit (Semesi et al, 2009).…”

Section: Physicochemical Conditionsmentioning

confidence: 89%

“…Seagrass systems routinely experience highly variable environmental conditions relative to coral reefs, such as reduced pH and increased temperature (Semesi et al, 2009;Challener et al, 2016), which could be critical in shaping resident coral communities. Studies of corals living among these high-variability systems can therefore also provide insight into which coral species are able to successfully acclimatize or adapt to survive under such conditions (Barshis, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Coral Community Structure and Recruitment in Seagrass Meadows

et al. 2017

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Coral communities are increasingly found to populate non-reef habitats prone to high environmental variability. Such sites include seagrass meadows, which are generally not considered optimal habitats for corals as a result of limited suitable substrate for settlement and substantial diel and seasonal fluctuations in physicochemical conditions relative to neighboring reefs. Interest in understanding the ability of corals to persist in non-reef habitats has grown, however little baseline data exists on community structure and recruitment of scleractinian corals in seagrass meadows. To determine how corals populate seagrass meadows, we surveyed the established and recruited coral community over 25 months within seagrass meadows at Little Cayman, Cayman Islands. Simultaneous surveys of established and recruited coral communities at neighboring back-reef sites were conducted for comparison. To fully understand the amount of environmental variability to which corals in each habitat were exposed, we conducted complementary surveys of physicochemical conditions in both seagrass meadows and back-reefs. Despite overall higher variability in physicochemical conditions, particularly pH, compared to the back-reef, 14 coral taxa were capable of inhabiting seagrass meadows, and multiple coral families were also found to recruit to these sites. However, coral cover and species diversity, richness, and evenness were lower at sites within seagrass meadows compared to back-reef sites. Although questions remain regarding the processes governing recruitment, these results provide evidence that seagrass beds can serve as functional habitats for corals despite high levels of environmental variability and suboptimal conditions compared to neighboring reefs.

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Section: Physicochemical Conditionssupporting

confidence: 79%

Section: Physicochemical Conditionssupporting

confidence: 77%

Section: Physicochemical Conditionsmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

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Coral Community Structure and Recruitment in Seagrass Meadows

et al. 2017

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“…While this study provides a point of reference for how seagrass beds can modify carbonate chemistry, determining the effects of macrophytes on acidification is challenging due to the extreme spatial and temporal variability of carbonate chemistry in these zones (Hendriks et al, 2014Krause-Jensen et al, 2015;Challener et al, 2016). A multitude of factors such as seagrass epiphyte communities, heterotrophic respiration, tidal exchange, groundwater flux, and riverine input all contribute in modifying carbonate chemistry on various spatial and temporal scales.…”

Section: Variations Of Carbonate Chemistry In Seagrass Bedsmentioning

confidence: 99%

Moderate Increase in TCO2 Enhances Photosynthesis of Seagrass Zostera japonica, but Not Zostera marina: Implications for Acidification Mitigation

2017

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Photosynthesis and respiration are vital biological processes that shape the diurnal variability of carbonate chemistry in nearshore waters, presumably ameliorating (daytime) or exacerbating (nighttime) short-term acidification events, which are expected to increase in severity with ocean acidification (OA). Biogenic habitats such as seagrass beds have the capacity to reduce CO 2 concentration and potentially provide refugia from OA. Further, some seagrasses have been shown to increase their photosynthetic rate in response to enriched total CO 2 (TCO 2 ). Therefore, the ability of seagrass to mitigate OA may increase as concentrations of TCO 2 increase. In this study, we exposed native Zostera marina and non-native Zostera japonica seagrasses from Padilla Bay, WA (USA) to various levels of irradiance and TCO 2 . Our results indicate that the average maximum net photosynthetic rate (P max ) for Z. japonica as a function of irradiance and TCO 2 was 3x greater than Z. marina when standardized to chlorophyll (360 ± 33 µmol TCO 2 mg chl −1 h −1 and 113 ± 10 µmol TCO 2 mg chl −1 h −1 , respectively). Additionally, Z. japonica increased its P max ∼50% when TCO 2 increased from ∼1,770 to 2,051 µmol TCO 2 kg −1 . In contrast, Z. marina did not display an increase in P max with higher TCO 2 , possibly due to the variance of photosynthetic rates at saturating irradiance within TCO 2 treatments (coefficient of variation: 30-60%) relative to the range of TCO 2 tested. Our results suggest that Z. japonica can affect the OA mitigation potential of seagrass beds, and its contribution may increase relative to Z. marina as oceanic TCO 2 rises. Further, we extended our empirical results to incorporate various biomass to water volume ratios in order to conceptualize how these additional attributes affect changes in carbonate chemistry. Estimates show that the change in TCO 2 via photosynthetic carbon uptake as modeled in this study can produce positive diurnal changes in pH and aragonite saturation state that are on the same order of magnitude as those estimated for whole seagrass systems. Based on our results, we predict that seagrasses Z. marina and Z. japonica both have the potential to produce short-term changes in carbonate chemistry, thus offsetting anthropogenic acidification when irradiance is saturating.

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Ocean pH time‐series and drivers of variability along the northern Channel Islands, California, USA

Hofmann

2016

Limnology & Oceanography

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Eastern boundary current systems (EBCSs) experience dynamic fluctuations in seawater pH due to coastal upwelling and primary production. The lack of high-resolution pH observations in EBCSs limits the ability to relate field pH exposures to performance of coastal marine species under future ocean change (acidification, warming). This 3-yr study describes spatio-temporal pH variability across the northern Channel Islands, along a persistent temperature gradient (1-48C) within the eastern boundary California Current System. pH and Conductivity, Temperature, Depth, and Oxygen sensors were deployed on island piers in eelgrass and kelp habitat and on a subtidal mooring. Due to event-scale primary production, the temperature gradient across the islands did not manifest in a pH gradient. We resolved spatial pH variability on diel (DpH T 0.05-0.2: photosynthesis), event-scale (DpH T <0.1-0.2: upwelling, phytoplankton blooms, wind relaxation), and seasonal (DpH T 0.06: warming) time frames. In the kelp forest, summer mean pH T (8.01-8.02) and magnitude of diel pH T cycles (DpH T 0.12-0.10) were comparable year-to-year, despite 2.18C warming from 2012 to 2014. Compared to nearby mainland sites, the northern Channel Islands experienced few low pH events. The majority of pH T observations were >7.9. The lowest pH observations (>1 SD below mean pH T ) occurred under either warm (respiration during warm nights) or cold (advection of upwelled water) temperatures. We emphasize the importance of incorporating site-specific environmental variability in studies of ocean change biology, particularly in the design of multistressor experiments.Coastal marine ecosystems are complex environments with spatio-temporal variability in productivity and bulk water mass movement. Physical and biological processes give rise to spatially unique pH-seascapes and are expected to change with climate change Hauri et al. 2013;Hoegh-Guldberg et al. 2014;Takeshita et al. 2015). Particularly, eastern boundary current systems (EBCSs) are predicted to be one of the first coastal ecosystems to cross thresholds of ocean acidification due to coastal upwelling (Gruber et al. 2012). While upwelling is a natural phenomenon, the associated onshore delivery of low pH water is exacerbated by ocean acidification (Feely et al. 2008).The heightened sensitivity of EBCSs to ocean change has already been realized in economic losses of shellfish production (Barton et al. 2012). The intensity of winds that are favorable to upwelling has increased in EBCSs (Sydeman et al. 2014) and upwelling events are predicted to increase in duration and strength with future climate change (Wang et al. 2015). As upwelling replenishes surface waters with nutrients yielding phytoplankton blooms that draw pCO 2 down to below atmospheric equilibrium (Hales et al. 2005), changes in upwelling may also alter coastal pH variability through influences on primary production in the future. Our understanding of present-day patterns in coastal carbon chemistry is often underdescribed making...

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Variability of the carbonate chemistry in a shallow, seagrass-dominated ecosystem: implications for ocean acidification experiments

Cited by 55 publications

References 43 publications

Coral Community Structure and Recruitment in Seagrass Meadows

Coral Community Structure and Recruitment in Seagrass Meadows

Moderate Increase in TCO2 Enhances Photosynthesis of Seagrass Zostera japonica, but Not Zostera marina: Implications for Acidification Mitigation

Ocean pH time‐series and drivers of variability along the northern Channel Islands, California, USA

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