Coral reef carbonate chemistry variability at different functional scales

There is a growing recognition for the need to understand how seawater carbonate chemistry over coral reef environments will change in a high-CO2 world to better assess the impacts of ocean acidification on these valuable ecosystems. Coral reefs modify overlying water column chemistry through biogeochemical processes such as net community organic carbon production (NCP) and calcification (NCC). However, the relative importance and influence of these processes on seawater carbonate chemistry vary across multiple functional scales (defined here as space, time, and benthic community composition), and have not been fully constrained. Here, we use Bermuda as a case study to assess (1) spatiotemporal variability in physical and chemical parameters along a depth gradient at a rim reef location, (2) the spatial variability of total alkalinity (TA) and dissolved inorganic carbon (DIC) over distinct benthic habitats to infer NCC:NCP ratios [< several km2; rim reef vs. seagrass and calcium carbonate (CaCO3) sediments] on diel timescales, and (3) compare how TA-DIC relationships and NCC:NCP vary as we expand functional scales from local habitats to the entire reef platform (10’s of km2) on seasonal to interannual timescales. Our results demonstrate that TA-DIC relationships were strongly driven by local benthic metabolism and community composition over diel cycles. However, as the spatial scale expanded to the reef platform, the TA-DIC relationship reflected processes that were integrated over larger spatiotemporal scales, with effects of NCC becoming increasingly more important over NCP. This study demonstrates the importance of considering drivers across multiple functional scales to constrain carbonate chemistry variability over coral reefs.

Continue reading ‘Coral reef carbonate chemistry variability at different functional scales’

Acidification at the surface in the East Sea: a coupled climate-carbon cycle model study

This modeling study investigates the impacts of increasing atmospheric CO2 concentration on acidification in the East Sea. A historical simulation for the past three decades (1980 to 2010) was performed using the Hadley Centre Global Environmental Model (version 2), a coupled climate model with atmospheric, terrestrial and ocean cycles. As the atmospheric CO2 concentration increased, acidification progressed in the surface waters of the marginal sea. The acidification was similar in magnitude to observations and models of acidification in the global ocean. However, in the global ocean, the acidification appears to be due to increased in-situ oceanic CO2 uptake, whereas local processes had stronger effects in the East Sea. pH was lowered by surface warming and by the influx of water with higher dissolved inorganic carbon (DIC) from the northwestern Pacific. Due to the enhanced advection of DIC, the partial pressure of CO2 increased faster than in the overlying air; consequently, the in-situ oceanic uptake of CO2 decreased.

Continue reading ‘Acidification at the surface in the East Sea: a coupled climate-carbon cycle model study’

The effects of ocean acidification on feeding and contest behaviour by the beadlet anemone Actinia equina

Increasing concentrations of atmospheric carbon dioxide are causing oceanic pH to decline worldwide, a phenomenon termed ocean acidification. Mounting experimental evidence indicates that near-future levels of CO2 will affect calcareous invertebrates such as corals, molluscs and gastropods, by reducing their scope for calcification. Despite extensive research into ocean acidification in recent years, the effects on non-calcifying anthozoans, such as sea anemones, remain little explored. In Western Europe, intertidal anemones such as Actinia equina are abundant, lower trophic-level organisms that function as important ecosystem engineers. Changes to behaviours of these simple predators could have implications for intertidal assemblages. This investigation identified the effects of reduced seawater pH on feeding and contest behaviour by A. equina. Video footage was recorded for A. equina feeding at current-day seawater (pH 8.1), and the least (pH 7.9) and most (pH 7.6) severe end-of-century predictions. Footage was also taken of contests over ownership of space between anemones exposed to reduced pH and those that were not. No statistically significant differences were identified in feeding duration or various aspects of contest behaviour including initiating, winning, inflating acrorhagi, inflicting acrorhagial peels and contest duration. Multivariate analyses showed no effect of pH on a combination of these variables. This provides contrast with other studies where anemones with symbiotic algae thrive in areas of natural increased acidity. Thus, novel experiments using intraspecific contests and resource-holding potential may prove an effective approach to understand sub-lethal consequences of ocean acidification for A. equina, other sea anemones and more broadly for marine ecosystems.

Continue reading ‘The effects of ocean acidification on feeding and contest behaviour by the beadlet anemone Actinia equina’

Boosted nutritional quality of food by CO2 enrichment fails to offset energy demand of herbivores under ocean warming, causing energy depletion and mortality

Highlights

• We tested if energy transfer via feeding is boosted under future seawater conditions.
• Energy budget of herbivores and nutritional quality of their food were determined.
• Energy budget raised by feeding on the more nutritious food under ocean acidification.
• When combined with warming, however, mass mortality occurred due to energy depletion.
• Enhanced food quality inadequately offsets the energy demand under ocean warming.

Abstract

The CO2-boosted trophic transfer from primary producers to herbivores has been increasingly discovered at natural CO2 vents and in laboratory experiments. Despite the emerging knowledge of this boosting effect, we do not know the extent to which it may be enhanced or dampened by ocean warming. We investigated whether ocean acidification and warming enhance the nutritional quality (C:N ratio) and energy content of turf algae, which is speculated to drive higher feeding rate, greater energy budget and eventually faster growth of herbivores. This proposal was tested by observing the physiological (feeding rate, respiration rate and energy budget) and demographic responses (growth and survival) of a common grazing gastropod (Phasianella australis) to ocean acidification and warming in a 6-month mesocosm experiment. Whilst we observed the boosting effect of ocean acidification and warming in isolation on the energy budget of herbivores by either increasing feeding rate on the more nutritious algae or increasing energy gain per feeding effort, their growth and survival were reduced by the sublethal thermal stress under ocean warming, especially when both climate change stressors were combined. This reduced growth and survival occurred as a consequence of depleted energy reserves, suggesting that the boosting effect via trophic transfer might not sufficiently compensate for the increased energy demand imposed by ocean warming. In circumstances where ocean acidification and warming create an energy demand on herbivores that outweighs the energy enhancement of their food (i.e. primary producers), the performance of herbivores to control their blooming resources likely deteriorates and thus runaway primary production ensues.

Continue reading ‘Boosted nutritional quality of food by CO2 enrichment fails to offset energy demand of herbivores under ocean warming, causing energy depletion and mortality’

Call for applications: scientific diving summer school in the Aeolian Archipelago, Italy 19-27 September 2018

Deadline for applications: 2 July 2018!

The school of Panarea is open to students, graduates, specialists, PhD and post-doctoral students in scientific disciplines and professionals engaged in study and management of the land/sea.

Topics will cover the geological characteristics of this unique active volcanic area, its bioligical components adapted to natural ocean acidification in the local vent systems, and hydrothermal fluid characterization.

Participants will be trained in multi-parameter monitoring techniques and definition of experimental protocols for the sampling and study of the planktonic and benthic ecosystem, with special focus on assessing effects of climate change and ocean acidification in organisms, communities and habitat.

Continue reading ‘Call for applications: scientific diving summer school in the Aeolian Archipelago, Italy 19-27 September 2018’

Pacific in peril: Micronesia’s food security, development, and health under a changing climate

This thesis focuses on food security in Micronesian Island nations and how the effects of climate change are detrimental to the region’s fisheries resources and agricultural production. Because the Micronesian islands are on the forefront of climate change, the effects of ocean acidification, rising sea levels, and higher mean surface areas pose immediate risks to the region’s food security. Not only does climate change threaten both sources of the region’s food – fisheries and traditional agriculture – but includes ramifications for economic development, environmental conservation, and public health. Each island nation in the Pacific is entitled to an Exclusive Economic Zone (EEZ). Because most of the world’s tuna stocks are concentrated in the Western Pacific, Pacific Island Countries (PIC) derive a significant portion of government revenue from selling tuna fishing licenses to countries such as Australia, China, Japan, and the US. Chapter 1 covers a brief history of the existing food systems in the Micronesian islands and pertinent data on the Micronesian islands’ climate, economy, geography, and health. Chapter 2 delves into climate change impacts on the islands’ terrestrial and marine ecology and the subsequent effects on island nations’ food sources both through agriculture and fisheries. Chapter 3 assesses the economic impacts – direct, indirect, and intangible costs – associated with the vulnerable food systems of island nations. Chapter 4 examines the resulting impacts on the nations’ overall public health conditions due to the disruptions in the vulnerable food systems. Chapter 5 poses several policy recommendations that address sustainable development, climate adaptation, and economic development. Overall, the overlapping lens of ecology, economics, and public health are used in exploring the impacts of climate change on food security on the Micronesian island nations.
Continue reading ‘Pacific in peril: Micronesia’s food security, development, and health under a changing climate’

Job opportunity: biological technician (Kodiak, Alaska)

Description

Ocean Associates, Inc. (OAI) is seeking a Biological Technician to provide support to the NOAA National Marine Fisheries Service (NMFS) Alaska Fisheries Science Center (AFSC), in Kodiak, AK. OAI supplies personnel support services on contract to government and industry clients for marine fisheries and protected species. This is a position to support research aimed at developing culturing techniques for crustaceans. The work will involve daily upkeep of a seawater laboratory facility and animal care at that facility, as well as assisting with the set up and running of experiments examining the effects of ocean acidification on Alaskan crab species. In addition, this position will involve assisting with routine seawater monitoring in the facility, and will also assist with the collection of crab data in field work. This is an excellent opportunity for a person with good laboratory and animal care skills to work with important fishery species, and to live in Kodiak, AK.

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Ocean acidification in the IPCC AR5 WG II

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