Posts Tagged 'field'

Evaluating the sensor-equipped autonomous surface vehicle C-Worker 4 as a tool for identifying coastal ocean acidification and changes in carbonate chemistry

The interface between land and sea is a key environment for biogeochemical carbon cycling, yet these dynamic environments are traditionally under sampled. Logistical limitations have historically precluded a comprehensive understanding of coastal zone processes, including ocean acidification. Using sensors on autonomous platforms is a promising approach to enhance data collection in these environments. Here, we evaluate the use of an autonomous surface vehicle (ASV), the C-Worker 4 (CW4), equipped with pH and pCO2 sensors and with the capacity to mount additional sensors for up to 10 other parameters, for the collection of high-resolution data in shallow coastal environments. We deployed the CW4 on two occasions in Belizean coastal waters for 2.5 and 4 days, demonstrating its capability for high-resolution spatial mapping of surface coastal biogeochemistry. This enabled the characterisation of small-scale variability and the identification of sources of low pH/high pCO2 waters as well as identifying potential controls on coastal pH. We demonstrated the capabilities of the CW4 in both pre-planned “autonomous” mission mode and remote “manually” operated mode. After documenting platform behaviour, we provide recommendations for further usage, such as the ideal mode of operation for better quality pH data, e.g., using constant speed. The CW4 has a high power supply capacity, which permits the deployment of multiple sensors sampling concurrently, a shallow draught, and is highly controllable and manoeuvrable. This makes it a highly suitable tool for observing and characterising the carbonate system alongside identifying potential drivers and controls in shallow coastal regions.

Continue reading ‘Evaluating the sensor-equipped autonomous surface vehicle C-Worker 4 as a tool for identifying coastal ocean acidification and changes in carbonate chemistry’

Retrieving monthly and interannual total-scale pH (pHT) on theEast China Sea shelf using an artificial neural network:ANN-pHT-v1 (update)

While our understanding of pH dynamics has strongly progressed for open-ocean regions, for marginal seas such as the East China Sea (ECS) shelf progress has been constrained by limited observations and complex interactions between biological, physical and chemical processes. Seawater pH is a very valuable oceanographic variable but not always measured using high-quality instrumentation and according to standard practices. In order to predict total-scale pH (pH(T)) and enhance our understanding of the seasonal variability of pHT on the ECS shelf, an artificial neural network (ANN) model was developed using 11 cruise datasets from 2013 to 2017 with coincident observations of pHT, temperature (T), salinity (S), dissolved oxygen (DO), nitrate (N), phosphate (P) and silicate (Si) together with sampling position and time. The reliability of the ANN model was evaluated using independent observations from three cruises in 2018, and it showed a root mean square error accuracy of 0.04. The ANN model responded to T and DO errors in a positive way and S errors in a negative way, and the ANN model was most sensitive to S errors, followed by DO and T errors. Monthly water column pHT for the period 2000-2016 was retrieved using T, S, DO, N, P and Si from the Changjiang biology Finite-Volume Coastal Ocean Model (FVCOM). The agreement is good here in winter, while the reduced performance in summer can be attributed in large part to limitations of the Changjiang biology FVCOM in simulating summertime input variables.

Continue reading ‘Retrieving monthly and interannual total-scale pH (pHT) on theEast China Sea shelf using an artificial neural network:ANN-pHT-v1 (update)’

Estuarine conditions more than pH modulate the physiological flexibility of mussel Perumytilus purpuratus populations

Highlights

  • Living under estuarine conditions causes physiological stress.
  • Estuarine conditions more than pH modulated the mussel performance and phenotypic plasticity.
  • Environmental variability of the habitat determines the phenotypic plasticity.
  • Environmental conditions of native habitats define the sensibility to climate change stressors.

Abstract

Coasts and their marine biota are exposed to major environmental heterogeneity as a consequence of natural drivers and anthropogenic stressors. Here, individuals of the mussel Perumytilus purpuratus from two different geographical populations exposed to contrasting environmental conditions (i.e. estuarine versus open coastal conditions) were used in a reciprocal transplant and a laboratory experiment in order to differential levels of local adaptation to their native sites, and sensibility to ocean acidification. After characterizing environmentally the two study sites, a set of life-history traits, as well as an estimated of the level of phenotypic plasticity were determined for both mussel populations. From the reciprocal transplant experiment, we observed that mussels originally coming from the estuarine habitat exhibited a distinctive performance pattern usually associated to physiological stress (i.e. higher metabolic rates, lower calcification and growth rates) leading also to important physiological trade-offs, and higher levels of phenotypic plasticity. Alternatively, mussels originating from the open coastal site showed lower physiological phenotypic plasticity suggesting a high grade of local adaptation. Contrary to expected, both populations responded very similar to lower pH conditions (i.e. increased metabolic rates with no important effects on growth and calcification, and lower physiological phenotypic plasticity). The study results indicated that overall estuarine conditions more than isolated pH would be modulating the performance and the level of phenotypic plasticity of the different P. purpuratus geographical populations studied. Our study also emphasizes the necessity of characterizing phenotypic plasticity under multiple-driver environments in order to cast more accurate predictions about the susceptibility of marine biota to future climate stressors such as the ocean acidification.

Continue reading ‘Estuarine conditions more than pH modulate the physiological flexibility of mussel Perumytilus purpuratus populations’

Decoupling salinity and carbonate chemistry: low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels

The Baltic Sea has a salinity gradient decreasing from fully marine (> 25) in the West to below 7 in the Central Baltic Proper. Reef forming mytilid mussels exhibit decreasing growth when salinity < 11, however the mechanisms underlying reduced calcification rates in dilute seawater are not fully understood. In fact, both [HCO3] and [Ca2+] also decrease with salinity, challenging calcifying organisms through CaCO3 undersaturation (Ω ≤ 1) and unfavourable ratios of calcification substrate (Ca2+ and HCO3) to inhibitor (H+). In this study we assessed the impact of isolated individual factors (salinity, [Ca2+], [HCO3] and pH) on calcification and growth of mytilid mussel populations along the Baltic salinity gradient. Laboratory experiments rearing juvenile Baltic Mytilus at a range of salinities (6, 11 and 16), HCO3 concentrations (300–2100 µmol kg−1) and Ca2+ concentrations (0.5–4 mmol kg−1) were coupled with field monitoring in three Baltic mussel reefs. Results reveal that as individual factors, low [HCO3], pH and salinity cannot explain low calcification rates in the Baltic Sea. Calcification rates are impeded when Ωaragonite ≤ 1 or the substrate inhibitor ratio ≤ 0.7, primarily due to [Ca2+] limitation which corresponds to a salinity of ca. 11. Increased food availability may be able to mask these negative impacts, but not when seawater conditions are permanently adverse, as observed in two Baltic reefs at salinities < 11. Future climatic models predict rapid desalination of the southwest and Central Baltic and potentially a reduction in [Ca2+] which may lead to a westward distribution shift of marine calcifiers. It is therefore vital to understand the mechanisms by which the ionic composition of seawater impacts bivalve calcification for better predicting the future of benthic Baltic ecosystems.

Continue reading ‘Decoupling salinity and carbonate chemistry: low calcium ion concentration rather than salinity limits calcification in Baltic Sea mussels’

A unique diel pattern in carbonate chemistry in the seagrass meadows of Dongsha island: implications for ocean acidification buffering

In contrast to most seagrass meadows where seawater carbonate chemistry generally shows strong diel variations with a higher pH during the daytime and a lower pH during nighttime due to the alternation in photosynthesis and respiration, the seagrass meadows of the inner lagoon on Dongsha Island had a unique diel pattern with an extremely high pH across a diel cycle. We suggest that this distinct diel pattern in pH was a result of a combination of total alkalinity (TA) production through the coupling of aerobic/anaerobic respiration and carbonate dissolution in the sediments and dissolved inorganic carbon consumption through the high productivity of seagrasses in overlying seawaters. The confinement of the semienclosed inner lagoon may hamper water exchange and seagrass detritus export to the adjacent open ocean, which may provide an ideal scenario for sedimentary TA production and accumulation, thereby forming a strong capacity for seagrass meadows to buffer ocean acidification.

Continue reading ‘A unique diel pattern in carbonate chemistry in the seagrass meadows of Dongsha island: implications for ocean acidification buffering’

Ecosystem status report of the California current for 2019–20: a summary of ecosystem indicators compiled by the California current integrated ecosystem assessment team (CCIEA)


This document is an expansion of the ecosystem status report (ESR) provided by the California Current Integrated Ecosystem Assessment Team (CCIEA Team) to the Pacific Fishery Management Council (PFMC) in March 2020 (Harvey et al. 2020). The CCIEA Team provides ESRs annually to PFMC, as one component of the overall CCIEA goal of providing quantitative, integrative science tools, products, and synthesis in support of a more holistic (ecosystem-based) approach to managing marine resources in the California Current. The ESR features a suite of indicators codeveloped by the CCIEA Team and PFMC. The suite of indicators was initially identified in 2009, and has been refined and updated over the years to best capture the current state of the California Current ecosystem (CCE). The analyses in this document represent our best understanding of environmental, ecological, and socioeconomic conditions in this ecosystem roughly through late 2019 and early 2020. Because the time required to process data varies for different indicators, some of the resulting time series are slightly more up-to-date than others. The time series for some indicators (snowpack, sea lion reproduction and pup growth, seabirds, fishery landings, fishery revenue, and nonfishing human activities) have been updated since the March 2020 report to PFMC (Harvey et al. 2020).

Continue reading ‘Ecosystem status report of the California current for 2019–20: a summary of ecosystem indicators compiled by the California current integrated ecosystem assessment team (CCIEA)’

Coastal ocean acidification: dynamics and potential to affect marine mollusks

Coastal marine ecosystems are both ecologically and economically productive, and as human coastal populations expand, these critical habitats have become subject to a suite of anthropogenic stressors. During the past century, the progressive rise in levels of atmospheric carbon dioxide (CO2) entering world oceans has decreased ocean pH and caused ocean acidification. An additional and often overlooked cause of acidification in coastal zones is the production of CO2 via microbial degradation of organic matter. Nutrient loading in coastal ecosystems facilitates enhanced algal productivity and the subsequent decomposition of this algal biomass reduces oxygen levels and can promote hypoxia. The precise temporal and spatial dynamics of acidification and hypoxia as well as their potential effects on resource bivalves are not well described in most coastal waters. Here, to evaluate the status of aquatic acidification in coastal systems, I examine the seasonal, diel, and high-resolution spatiotemporal dynamics of carbonate chemistry and dissolved oxygen (DO) over a six year period in multiple northeast US estuaries and across multiple coastal habitats that host keystone marine species while concurrently quantifying the growth and survival of multiple early life stage suspension feeding bivalves. To assess the potential for acidification in eutrophic estuaries, the levels of DO, pH, the partial pressure of carbon dioxide (pCO2), and the saturation state of aragonite (ΩAr) were iv horizontally and vertically assessed during the onset, peak, and demise of low oxygen conditions in systems across the northeast US including Narragansett Bay (RI), Long Island Sound (CTNY), Jamaica Bay (NY), and Hempstead Bay (NY). Hypoxic waters and/or regions in close proximity to sewage discharge had extremely high levels of pCO2, (> 3,000 µatm), acidic pH (< 7.0), and were undersaturated with respect to aragonite (ΩAr < 1). The close spatial and temporal correspondence between DO and pH and the occurrence of extremes in these conditions in regions with the most intense nutrient loading indicated that they were driven primarily by enhanced microbial respiration relative to physical exchange processes. Next, I quantified the temporal and spatial dynamics of DO, carbonate chemistry, and net ecosystem metabolism (NEM) from spring through fall in multiple, distinct, temperate estuarine habitats: seagrass meadows, salt marshes, an open water estuary, and a shallow water habitat dominated by benthic macroalgae. All habitats displayed clear diurnal patterns of pH and DO, with minimums observed during early morning and maximums observed in the afternoon where diel ranges in pH and DO varied by site. NEM across habitats ranged from net autotrophic (macroalgae and seagrass) to metabolically balanced (open water) and net heterotrophic (salt marsh). Each habitat examined exhibited distinct buffering capacities that varied seasonally and were modulated by adjacent biological activity and variations in total alkalinity (TA) and dissolved inorganic carbon (DIC). I utilized continuous monitoring devices to characterize the diurnal dynamics of DO and carbonate chemistry from spring through fall across two, temperate eutrophic estuaries, western Long Island Sound and Jamaica Bay, NY. Vertical dynamics were resolved using an underway towing profiler and an automated stationary profiling unit. During the study, high rates of respiration in surface and bottom waters (> -0.2 mg O2 L -1 h -1 ) were observed where ephemeral surface water algal blooms caused brief periods of basification and supersaturation of DO that v were succeeded by periods of acidification and hypoxia. Diurnal vertical profiles demonstrated that oxic surface waters saturated with respect to calcium carbonate (aragonite) during the day transitioned to being unsaturated and hypoxic at night. Evidence is presented that, beyond respiration, nitrification of surface water strongly influenced by sewage discharge and oxidation processes in sediments can also contribute to acidification in these estuaries. Finally, the growth and survival of three bivalve species (Argopecten irradians, Crassostrea virginica, Mytilus edulis) were examined in an in-situ CO2 enrichment system deployed in a seagrass meadow and an open water estuary, and across a natural eutrophication gradient in Jamaica Bay, NY. In the seagrass meadow, the growth and survival of C. virginica and A. irradians significantly declined during the late summer in response to CO2 gas injection. During the open water CO2 enrichment experiment, all three species of bivalves exhibited depressed growth within the acidified chambers with no significant difference in mortality between treatments. In Jamaica Bay, dense phytoplankton blooms in the early summer decreased CO2 and increased DO creating spatial refuges for bivalves where growth rates were enhanced, but by the late summer, trends reversed as bivalve growth was depressed at these same locations due to the onset of acidification and hypoxia. Collectively, this dissertation has identified coastal ocean acidification as a symptom of eutrophication that can threaten marine bivalve populations.

Continue reading ‘Coastal ocean acidification: dynamics and potential to affect marine mollusks’

Development of an autonomous dissolved inorganic carbon sensor for oceanic measurements

Since the industrial revolution the CO2 concentrations in the atmosphere have increased from 280 ppm to over 400 ppm, and each year the oceans take up approximately 25% of the annually emitted anthropogenic CO2. This increase in CO2 in the oceans has had a measure able impact on the marine carbonate system, and the resultant increase in the acidity of the ocean is a potential stressor for a range of ecosystems. In order to fully quantify the marine carbonate system there are four variables that can be measured, these are dissolved inorganic carbon (DIC), pH, total alkalinity and partial pressure of CO2. By measuring two of the four variables the others can be determined. Of these variables DIC is the only one without either an underway or in situ sensor, despite being one half of the preferred pairs for observing the carbonate system. To address this technological gap and increase the measurement coverage there is a clear need for an autonomous sensor capable of making quality measurements while having a robust, small physical size, and low power requirements. Presented here are the results of developmental work that has led to a full ocean depth rated autonomous DIC sensor, based on a microfluidic “Lab On Chip” (LOC) design. The final version of the DIC LOC sensor operates by acidifying < 1 ml of seawater, converting the DIC to CO2, which is diffused across a gas permeable membrane into an acceptor solution. The CO2 reacts with the acceptor resulting in a conductivity drop that is measured using a Capacitively Coupled Contactless Conductivity Detector (C4D). Each measurement takes ~15 minutes and the sensor can be set up to perform calibrations in situ. Laboratory testing demonstrated this system has a precision of < 1 µmol kg-1. The sensor was deployed as part of a large EU project aiming to detect a simulated sub-seabed leak of CO2. Over multiple deployments in the North Sea the sensor collected data used to locate the leak. A number of field tests have established the sensor has a precision of < 10 µmol kg-1. This work has demonstrated that this sensor offers potential to fill the current technological gap and collect data that will enhance understanding of the marine carbonate system.

Continue reading ‘Development of an autonomous dissolved inorganic carbon sensor for oceanic measurements’

Seasonal variations of carbonate chemistry at two Western Atlantic coral reefs

Time series from open ocean fixed stations have robustly documented secular changes in carbonate chemistry and long‐term ocean acidification (OA) trends as a direct response to increases in atmospheric carbon dioxide (CO2). However, few high‐frequency coastal carbon time series are available in reef systems, where most affected tropical marine organisms reside. Seasonal variations in carbonate chemistry at Cheeca Rocks (CR), Florida, and La Parguera (LP), Puerto Rico, are presented based on 8 and 10 years of continuous, high‐quality measurements, respectively. We synthesized and modeled carbonate chemistry to understand how physical and biological processes affect seasonal carbonate chemistry at both locations. The results showed that differences in biology and thermodynamic cycles between the two systems caused higher amplitudes at CR despite the shorter residence times relative to LP. Analyses based on oxygen and temperature‐normalized pCO2sw showed that temperature effects on pCO2sw at CR were largely counteracted by primary productivity, while thermodynamics alone explained a majority of the pCO2sw dynamics at LP. Heterotrophy dominated from late spring to fall, and autotrophy dominated from winter to early spring. Observations suggested that organic respiration decreased the carbonate mineral saturation state (Ω) during late summer/fall. The interactive effects between the inorganic and organic carbon cycles and the assumed effects of benthic metabolism on the water chemistry at both sites appeared to cause seasonal hysteresis with the carbonate chemistry. Improved integration of observational data to modeling approaches will help better forecast how physical and biogeochemical processes will affect Ω and carbonate chemistry in coastal areas.

Continue reading ‘Seasonal variations of carbonate chemistry at two Western Atlantic coral reefs’

Ocean acidification alters bacterial communities on marine plastic debris

Highlights

  • Plastic will act as a novel ecological habitat for microbial communities.
  • Plastics harbour taxonomically distinct microbial communities (“Plastisphere”).
  • Ocean acidification greatly influences the Plastisphere community composition.

Abstract

The increasing quantity of plastic waste in the ocean is providing a growing and more widespread novel habitat for microbes. Plastics have taxonomically distinct microbial communities (termed the ‘Plastisphere’) and can raft these unique communities over great distances. In order to understand the Plastisphere properly it will be important to work out how major ocean changes (such as warming, acidification and deoxygenation) are shaping microbial communities on waste plastics in marine environments. Here, we show that common plastic drinking bottles rapidly become colonized by novel biofilm-forming bacterial communities, and that ocean acidification greatly influences the composition of plastic biofilm assemblages. We highlight the potential implications of this community shift in a coastal community exposed to enriched CO2 conditions.

Continue reading ‘Ocean acidification alters bacterial communities on marine plastic debris’

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