Effects on the Pocillopora verrucosa microbiome when in contact with macroalgae under ocean acidification

Hard coral cover is in decline and this decline has generally coincided with macroalgal proliferation in coral reefs (Gardner et al. 2003, Cheal et al. 2010, De’ath et al. 2012). Coral degradation can be caused by many variables (Hoegh-Guldberg et al. 2007, Anthony et al. 2008, Mumby and Steneck 2008) but this study is focused on potential degradation due to direct competition with allelopathic macroalgae under the effects of future ocean acidification. Allelopathy is the use of chemicals for protection or competitive purposes. It has previously been shown that algae compete with corals through allelopathy, but not if allelopathy causes the microbiome of the coral to enter a diseased state, though there have been several cases of diseased microbiome states observed (Bourne et al. 2009, Mao-Jones et al. 2010, Meyer et al. 2014). As such, it is of interest to determine if the allelopathic competition from algae affects the coral microbiome, leading to a diseased state, and whether these interactions are exaggerated or effected by ocean acidification.

We hypothesize that macroalgal allelopathy effects the microbiome of the reefbuilding coral Pocillopora verrucosa and that these competitive interactions will be affected by the stressor of ocean acidification. We expect the latter because of previous evidence that increased pH causes stress to some species of corals (Anthony et al. 2008). To test this, we used a pre-established scale of algal allelopathy demonstrated in Rasher et al. (2011) and placed corals and algae in contact under ocean acidification conditions for 3 weeks before samples were processed for microbial taxonomy. The initial analyses have demonstrated no significant differences in the abundances of major microbial taxa compositions for the sampled coral microbiomes when in the presence of the various
allelopathic macroalgae, but these are preliminary findings. The data will require finer microbial analysis to determine whether or not there are any significant effects on the coral microbiomes.

Continue reading ‘Effects on the Pocillopora verrucosa microbiome when in contact with macroalgae under ocean acidification’

Propagation of uncertainties in mesocosm experiments on ocean acidification

Observations from different mesocosms exposed to the same treatment typically show variability that hinders the detection of potential treatments effects. To unearth relevant sources of variability, I developed and performed a model-based data analysis that simulates uncertainty propagation. I described how the observed divergence in the outcomes can be due to differences in experimentally unresolved ecological factors within same treatment replicates that get amplified over the course of the experiment. Three independent ocean acidification experiments on the response of phytoplankton to high CO2 concentrations in aquatic environments were used as tests cases. I first simulated the dynamics of the mean phytoplankton biomass in each treatment and detected acidification effects on the timing and intensity of the bloom in spite of the so far negative results obtained by statistical inference tools. By using the mean dynamics as reference for the uncertainty quantification, I showed that differences among replicates in parameters related to initial i) plankton community composition and ii) nutrient concentration can generate higher biomass variability than the response that can be attributed to the effect of elevated levels of CO2. I calculated confidence intervals for parameters and initial conditions. They can serve as estimation of the mesocosms tolerance thresholds below which uncertainties do not escalate into high outcomes variability. This information can improve the detection of treatment effects in next generation experimental designs and contributes to the ongoing discussion on the interpretation of controversial results in mesocosm experiments.

Continue reading ‘Propagation of uncertainties in mesocosm experiments on ocean acidification’

Assessment of net community production and calcification of a coral reef using a boundary layer approach

Coral reefs are threatened worldwide, and there is a need to develop new approaches to monitor reef health under natural conditions. Because simultaneous measurements of net community production (NCP) and net community calcification (NCC) are used as important indicators of reef health, tools are needed to assess them in situ. Here, we present the Benthic Ecosystem and Acidification Measurement System (BEAMS), to provide the first fully autonomous approach capable of sustained, simultaneous measurements of reef NCP and NCC under undisturbed, natural conditions on timescales ranging from tens of minutes to weeks. BEAMS combines the chemical and velocity gradient in the benthic boundary layer to quantify flux from the benthos for a variety of parameters to measure NCP and NCC. Here, BEAMS was used to measure these rates from two different sites with different benthic communities on the western reef terrace at Palmyra Atoll for two weeks in September, 2014. Measurements were made every ∼15 minutes. The trends in metabolic rates were consistent with the benthic communities between the two sites with one dominated by fleshy organisms and the other dominated by calcifiers (degraded and healthy reefs, respectively). This demonstrates the potential utility of BEAMS as a reef health monitoring tool. NCP and NCC were tightly coupled on timescales of minutes to days, and light was the primary driver for the variability of daily integrated metabolic rates. No correlation between CO2 levels and daily integrated NCC was observed, indicating that NCC at these sites were not significantly affected by CO2.

Continue reading ‘Assessment of net community production and calcification of a coral reef using a boundary layer approach’

Ontogenetic variability in the feeding behavior of a marine amphipod in response to ocean acidification

Global stressors like ocean acidification (OA) are expected to influence the quality or palatability of primary producers like algae. Such changes can trigger a response on algal consumers’ feeding strategies, and this response may not necessarily be the same for the consumers during the ontogeny. We used a mesocosm’s system to expose algae to current and projected OA conditions (390 and 1000 ppm, respectively) and then compared the feeding behavior and absorption efficiency of juvenile and adult stages of the amphipod Orchestoidea tuberculata. Specifically, we measured consumption rates (with and without a choice) and absorption efficiency on algae exposed and not exposed to OA. Our results show that OA affect the amphipod’s consumption and feeding preferences, and that these effects were related with the analyzed ontogenetic stage (juveniles versus adults). These results support the existence of an ontogenetic change in the response of this species and others similar marine invertebrates to OA, which highlight the need to incorporate different life stages in the study of OA or others global stressors.

Continue reading ‘Ontogenetic variability in the feeding behavior of a marine amphipod in response to ocean acidification’

Volunteer groups monitor ocean acidification in marine reserves

Photo credit: Surfrider

Photo credit: Surfrider

Researchers and community groups are teaming up on a new project along our coast to help monitor pH for detecting and characterizing the progression of ocean acidification in Oregon’s Marine Reserves. The collaboration, spearheaded by Oregon State University (OSU) and the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO), is teaming up with marine reserve community groups up and down the coast, including Surfrider’s Newport Chapter, to not only fill geographic gaps in scientific monitoring, but to also engage citizens in making measurements in their local coastal ecosystems to better understand this complex issue.

The Surfrider Foundation’s Newport Chapter recently joined the Redfish Rocks Community Team and the Nature Conservancy in adopting community monitoring sites within Oregon’s Marine Reserves as part of this new academic research and community collaboration. Project lead Francis Chan of OSU, who also chairs the West Coast Ocean Acidification and Hypoxia Science Panel (westcoastoah.org), is building off of previous academic research over the years through deployment of robust, low cost and high performance pH sensors which can be easily managed and maintained by citizens and volunteers.

Continue reading ‘Volunteer groups monitor ocean acidification in marine reserves’

Ocean acidification talk – Port Townsend, Washington State, 29 July 2016

PORT TOWNSEND — The Port Townsend Marine Science Center’s Marine Exhibit will host “Oceanography on the Dock” at the pier, 532 Battery Way, from noon to 1 p.m. Friday, July 29.

The oceanography field course for the public will focus on ocean acidification.

The event is free and open to the public.

To schedule a session for a larger group or at special times, email info(at)ptmsc.org.

Peninsula Daily News. Further information.

Coastal-ocean uptake of anthropogenic carbon (update)

Anthropogenic changes in atmosphere–ocean and atmosphere–land CO2 fluxes have been quantified extensively, but few studies have addressed the connection between land and ocean. In this transition zone, the coastal ocean, spatial and temporal data coverage is inadequate to assess its global budget. Thus we use a global ocean biogeochemical model to assess the coastal ocean’s global inventory of anthropogenic CO2 and its spatial variability. We used an intermediate resolution, eddying version of the NEMO-PISCES model (ORCA05), varying from 20 to 50 km horizontally, i.e. coarse enough to allow multiple century-scale simulations but finer than coarse-resolution models (∼  200 km) to better resolve coastal bathymetry and complex coastal currents. Here we define the coastal zone as the continental shelf area, excluding the proximal zone. Evaluation of the simulated air–sea fluxes of total CO2 for 45 coastal regions gave a correlation coefficient R of 0.8 when compared to observation-based estimates. Simulated global uptake of anthropogenic carbon results averaged 2.3 Pg C yr−1 during the years 1993–2012, consistent with previous estimates. Yet only 0.1 Pg C yr−1 of that is absorbed by the global coastal ocean. That represents 4.5 % of the anthropogenic carbon uptake of the global ocean, less than the 7.5 % proportion of coastal-to-global-ocean surface areas. Coastal uptake is weakened due to a bottleneck in offshore transport, which is inadequate to reduce the mean anthropogenic carbon concentration of coastal waters to the mean level found in the open-ocean mixed layer.

Continue reading ‘Coastal-ocean uptake of anthropogenic carbon (update)’


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