United States Geological Survey

Broad Overview of and Rationale for Ocean Acidification Work

The United States Geological Survey has no formal ocean acidification program or umbrella project designated solely as “ocean acidification,” but it does have projects that address ocean acidification issues and are relevant to the USGS mission. These projects are threaded through multiple USGS programs, including Coastal and Marine Geology and Ecosystems Programs. Guidance for USGS ocean acidification research is defined in two of the seven USGS mission area science strategies:  Climate and Land Use Change and Ecosystems. One major goal under the Ecosystems mission area is to advance the understanding of how various anthropogenic and natural drivers influence ecosystem change. In that capacity, USGS work, in collaboration with other Federal government and academic efforts, focuses on investigating the magnitude of ocean acidification in various ecosystems and the ecosystem impacts of ocean acidification, including the degradation of marine systems and effects on of ocean acidification on carbonate producing organisms.

Four science projects with tasks that the USGS has implemented since 2009 to advance the Federal response to ocean acidification include: Florida Shelf Ecosystems Response to Climate Change, Arctic Ocean Acidification, Coral Reef Ecosystem Study, and Exploring the Links between Coral Reefs and Mangroves. These projects are discussed further below and on the USGS ocean acidification website. Two technical projects that have been implemented are CO2calc, a software program that facilitates the study of ocean acidification by making carbon chemistry calculations easier to do, and the development of a pH photometer (light-sensitive machinery) for use in a variety of aquatic environments.

On-going Projects Related to Ocean Acidification

West Florida Shelf and Estuaries Ecosystems Response to Climate Change

Temperate and subtropical ocean regions are home to a diverse range of environmental conditions, habitats, species, and fisheries.  Scientists at the USGS are monitoring seawater chemistry associated with ocean acidification and benthic habitats on the Florida Shelf and its associated estuaries. Research under this project has four goals:

  • Fill datagaps in the Gulf of Mexico for carbon flux (measured via pCO2) and carbon system parameters, such as saturation state, so that resource managers can make informed natural resource management decisions related to ocean Global carbon chemistry models have generally neglected the Gulf of Mexico, a marginal but highly productive sea.  Existing data on carbon system parameters do not sufficiently address the spatial and temporal variability in the carbon system in this temperate to sub-tropical sea.  Working with Federal and academic partners, USGS has collected carbon chemistry data and is now undertaking a synthesis of these datasets as part of a NASA-funded project.
  • Conduct laboratory experiments to investigate the effect of ocean acidification on the growth of marine calcifying organisms that produce calcium carbonate sediments in temperate, subtropical, and tropical marine ecosystems, and model calcium carbonate production rates under different CO2 scenarios to predict the response of the organisms and sediment production over The process of calcium carbonate mineralization is essential in the formation of shells and other structures of many marine organisms such as shellfish, plankton, and algae. Laboratory research on the how ocean acidification may impact species suggests that the calcium carbonate mineralization processes is more expensive energetically under ocean acidification conditions. With increased ocean acidification, it is likely that many organisms that create calcium carbonate minerals to build their shells or other structures will be negatively affected. Calcium carbonate is also a major component in limestone and carbonate sands, resources that are critical to the resiliency of many of the beaches and coasts of the United States. Ocean acidification can cause a decrease in calcification and dissolution of carbonate sediments that may lead to erosion of underwater carbonate structures and increase the vulnerability of coastal communities to storms and seafloor habitat loss.
  • Address data gaps in coastal waters of the West Florida Shelf related to ocean acidification, and increase understanding of how ocean acidification affects estuarine and shallow shelf marine Shallow water cruises conducted by the USGS with Federal and state partners provide regional informationon the saturation state and pCO2 fluctuation at the seawater/air boundary using state-of-the-art techniques. Data from the State of Florida shellfish harvest areas are being evaluated for changes in estuarine water chemistry over the last two and a half decades.
  • Develop and maintain CO2calc, a software program that facilitates the study of ocean acidification by making carbon chemistry calculations easier to do, and initiate development of a new device for measuring pH. Advancement of pH measurements is fundamental to providing sufficient data on ocean carbon chemistry for understanding natural and anthropogenic variability and the signal of ocean USGS is working with academic partners to develop tools that are user friendly and inexpensive to facilitate wider access to data.

Arctic Ocean Acidification

With a fairly constant water temperature of 0°C, the Arctic Ocean has the ability to absorb carbon dioxide more readily than warmer waters. Ocean acidification may be occurring faster at the poles than other regions for several reasons:

  • Coldwater more readily absorbs CO2, lowering the pH of the water;
  • Added melt-water from glaciers and the ice cap and increased riverine input forces additional uptakeof CO2 in the Arctic Ocean;
  • Reduced sea-icecoverage results in more seawater exposure to and uptake of atmospheric CO2; and
  • Expanded ocean-surface area may, in turn, alter the production and decomposition of organic carbon, a complex process that plays an important role in ocean

Baseline data collected during cruises from 2010-2012 that USGS hosted or participated in provided over 30,000 records and more than doubled the existing data on the carbon chemistry of the Arctic Ocean.

These baseline data define an area the size of Montana within the Canada Basin that is already undersaturated with respect to aragonite—a calcium carbonate mineral associated with organisms that are important to the food web – which suggests that carbon chemistry conditions may already influence species in the region. USGS continues to collect ocean acidification monitoring data from Arctic waters by participating in regional cruises operated by other Federal agencies.

Coral Reefs

Coral reefs are vital to the long-term viability of tropical coastal communities, providing economic, recreational, and aesthetic value upon which coastal communities thrive. Coral reefs provide nurseries and habitat for commercially important fish species, sand for beaches, and protection from storm waves.  These coral reef services and resources depend on the ability of calcifying organisms to build the three-dimensional structure of the reef as they produce their calcium carbonate skeletons.  Ocean acidification can cause a decrease in calcification and dissolution of carbonate sediments that may lead to erosion of reef structure.  Researchers at the USGS are working with various Federal government and academic partners at a variety of locales around the globe to develop comprehensive records of modern and historical coral reef growth and calcification rates relative to changing seawater chemistry resulting from ocean acidification.  These records will provide the foundation for predicting future impacts of ocean acidification and sea-level rise on coral reef growth through the following actions:

  • Monitoring calcification and metabolism rates in living coral reef communities;
  • Monitoring growth rates of individual coral species;
  • Monitoring seawater chemistry associated with ocean acidification;
  • Measuring historic coral growth rates from coral cores relative to historic changes in seawater pH; and
  • Conducting field experiments to quantify the effect of predicted seawater pH and CO2 levels on coral reef growth and accumulation rates.

Exploring the Links between Coral Reefs and Mangroves

Risk analyses indicate that more than 90 percent of the world’s coral reefs will be threatened by climate change and local anthropogenic impacts by the year 2030 if no action is taken to curb carbon dioxide emissions.  Increasing temperatures and solar radiation cause coral bleaching that has resulted in extensive coral mortality. Increasing CO2 reduces seawater pH, slows coral growth, and may cause loss of coral reef structure. Management strategies to protect coral reefs in the face of ocean acidification include establishment of marine protected areas with environmental conditions that promote coral reef resiliency. Few coral reefs insensitive to the impacts of climate change and ocean acidification have been identified, however, and the factors that results in this resiliency are poorly defined. USGS researchers have characterized that mangroves can act as a refuge for corals from thermal stress and ocean acidification. In doing so, they have identified the first natural, non-reef refuge for corals from thermal stress and ocean acidification. This previously undocumented refuge for corals provides evidence for adaptation of coastal organisms and ecosystem transition due to recent climate change.

Activities on this work include:

  • Measurements of diurnal and seasonal variations in temperature, salinity, photosynthetically active radiation, and seawater chemistry (including dissolved oxygen and carbon system parameters);
  • Characterization of substrate parameters including grain size and mineralogy;
  • Examination of water circulation patterns in mangrove communities where scleractinian corals are growing attached to and under mangrove prop roots;
  • Inventories of coral species and quantification of incidences of coral bleaching, mortality, and recovery for two major reef-building corals, Colpophyllia natans and Diploria labyrinthiformis, growing in mangrove shaded and exposed (unshaded) areas; and
  • Identification and quantification of chemical, physical, and biological resiliency factors for mangrove-coral habitats.

Near-future Activities Related to Ocean Acidification (Planned within the Next 2 Years)

USGS will assess processes that are driving ocean acidification in the Gulf of Mexico and in the Florida Shelf and its associated estuaries. The Gulf of Mexico research will go hand-in-hand with NASA funded collaborative research on coastal carbon data synthesis using air-sea CO2 flux data.  Modeling of predicted changes in carbonate sediment production based on chemical and geological oceanographic data and biologic experiments will continue. Over the next two years, synthesis of Arctic Ocean carbon parameter data will continue, and new data will be acquired as funding permits. Through Landscape Conservation Cooperatives and in collaboration with Fish and Wildlife Service, USGS will address science-based conservation objectives and strategies related to ocean acidification.

In the Florida Shelf over the next two years, USGS will perform a transdisciplinary characterization of reef-scape scale processes affecting and affected by ocean acidification including:  high resolution measurement of spatial and temporal variation of carbonate system and associated parameters at the seafloor and throughout the water column, sedimentologic and mineralogic characteristics, high resolution changes in seafloor elevation relative to sea level rise using Sediment Elevation Tables, coral transplant studies, microbial population dynamics, and paleoecological reconstruction. Measurement and monitoring of fine-scale elevation changes on the Florida Keys Reef Tract using Sediment Elevation Tables will quantify structural loss (or gain) of reef habitat accumulation relative to sea level rise.

Maintenance of the software carbon calculator CO2calc and development of the pH photometer will continue as funding permits.

Far-future Activities Related to Ocean Acidification (Planned within the Next 3-5 Years)

Far-future plans for USGS ocean acidification-related activities include continued support of current activities, and future activities that result from partnerships and collaborations with other Federal, tribal, state, academic, and private institutions and build on existing capabilities and leveraging of resources.

Gaps in Portfolio of Activities Related to Ocean Acidification, Compared to Priorities Outlined in the Strategic Research Plan

The Strategic Research Plan is an accurate representation of current and planned ocean acidification- related activities in the USGS.

Untapped Opportunities Inside of Agency for Projects Related to Ocean Acidification

It is projected that degradation of coral reef and other coastline habitats due to ocean acidification will result in the inability of coral reef growth to keep up with rising sea level.  There are currently no monitoring programs for high-resolution changes in seafloor elevation.  USGS is performing the first  pilot study to use Sediment Elevation Table methods for fine scale measurement of loss or accretion of coastal habitats due to ecosystem transition relative to sea level rise and in context with the national coastline elevation database.  These results will form the basis for development of a new monitoring program to complement habitat, seawater chemistry, oceanographic, and ecosystem process studies on the impacts of ocean acidification that could be implemented in the future.

USGS geologic expertise remains virtually untapped as it related to ocean acidification.  For example, areas of knowledge related to ocean acidification include paleo-ecosystems, the processes of sedimentation and mineral formation, the composition of sediments, the geology of coastal ecosystems, and proxies for monitoring activities under projected environmental conditions.

Ideas for How Agency Could Work with Other Federal Agencies on Activities Related to Ocean Acidification

The USGS provides unique resources and expertise in geologic, oceanographic, and geochemical research and monitoring that complement other agencies’ activities and can be used to facilitate and leverage future research activities.

Areas Where Agency Mission is Being Inhibited by Knowledge Gaps that Fall out of Agency’s Purview

USGS would benefit from an improved numerical modeling of ocean acidification processes. USGS is collecting data that can be used to validate coastal ocean and ecosystem modeling activities, but resources limit production of models in house.





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