Cost of Coastal Carbon

Coastal ocean consists of interconnected ecosystems including estuaries, tidal wetlands and continental shelf. Carbon cycling within the coastal ocean is known to be a major component of global carbon budgets, as it acts as the connecting medium between terrestrial and oceanic systems. Carbon fluxes within these systems are greatly influenced by the changing climatic elements as well as anthropogenic influences. Understanding the nature of changes in the carbon fluxes is substantial for studying 21st-century carbon cycles.

The recent recognition of coastal contribution to the anthropogenic carbon budget has brought coastal carbon cycle shift into stark focus. Human activities have been greatly influential on the recent shift of coastal carbon cycle. The coastal ocean has become an atmospheric CO2 sink as well as a burial site for organic and inorganic carbon.

Riverine Carbon Influxes:

Coastal ocean carbon fluxes are correlated with riverine discharge which is affected by precipitation and temperature changes within a region. The extreme hydrological events, including high-intensity storms, play an important role in changing riverine carbon fluxes. The erosive power of these storms may result in increased particulate organic carbon (POC) as well as dissolved organic carbon (DOC) transport to the coastal ocean. While certainty is low, climate models predict an increasing frequency of intense hydrological events and thus an increase in the POC and DOC transport to the coastal ocean. DOC transport by a single storm can account for 40% of the annual DOC transport by riverine systems while large floods can export up to 90% of POC from uplands in decadal timescales.

Estuaries:

Estuaries are known as the transitional mediums between terrestrial and coastal environments which act as modulators of carbon fluxes between land and coastal ocean. Biogeochemical gradients are observed to be very strong in estuarine environments. A number of physical and environmental factors within estuarine environments affect the amount of organic and inorganic carbon fluxes including, estuarine geomorphology and controls on nutrient inputs.

DOC and POC in estuaries are formed through primary production in marine, terrestrial and estuarine environments. While, organic carbon production in estuarine environments are important contributors to carbon fluxes, loss of organic carbon is present in estuaries as microbial degradation, as well as photochemical oxidation, are at work. Estuaries are also known as modulators of organic carbon exports as unique reactivity of estuarine produced organic carbon has differing degradation times to important gases including CO2 and CH4. European estuaries CO2 emissions are important components of regional CO2 budgets. When the global area held by estuaries considered the disproportionate contribution to CO2 exchanges by these natural systems comes to stark focus.

Anthropogenic impacts on Coastal Carbon Cycle:

Changes in the land use and with-it waterway blockages, nutrient level alterations and climate change have made the differentiation between natural and anthropogenic drivers of carbon flux modifications. While the majority of anthropogenic factors affecting coastal carbon, fluxes are identified the quantitative contribution to changes are still uncertain.

The identification of direction and magnitude of human affected fluxes is fundamental to the understanding of terrestrial CO2 carbon sink. Recent studies have revealed that the change in land carbon storage modelled by IPCC could be an overestimation as a significant amount of carbon is stored in coastal ocean and sediments.

Land management is an important modifier of carbon exports in riverine ecosystems to coastal waters. These include agricultural practices, which have increased the sediment and thus particulate organic carbon transfer to the coastal ocean from terrestrial regions. However, this does not indicate any caused increase in carbon fluxes because much of particulate carbon is believed to be trapped by man-made reservoirs and dams as well as deposited to land.

Reservoirs reduced the particulate organic carbon fluxes by 90% compared to pre-anthropogenic particulate organic carbon transfer. Due to liming and hydrological modifications within the riverine systems, bicarbonate ion fluxes have been observed to increase by 40%. This believed to be a reason for differing chemical characteristics of agriculturally and naturally exported organic carbon. Dissolved inorganic carbon exports are also known to have increased due to anthropogenic acid addition to riverine environments.

While changing climatic patterns and environmental factors affecting carbon fluxes play an important role in decreased particulate organic carbon fluxes and future climatic changes are expected to alter carbon exports to a greater extent, human impacts play an integral role in alteration of the coastal ocean carbon fluxes. Changes in the physical environment including, river discharge, sea-level changes as well as storm frequency and intensities have altered the biochemical processes and CO2 exchanges between estuaries and the atmosphere and coastal ocean.

What to do:

Anthropogenic impact on the global carbon cycle and thus climatic balance has been studied through the years, however, the modification of the hydrological elements and their contribution to carbon cycle was undermined. With the help of recent studies, one can fully get the scoop of the magnitude of change induced within the hydrological environments by human populations. The advanced management and limitation of the anthropogenic impact on riverine environments and thus the coastal ocean is fundamental for the survival of the natural balance.

We have great impacts on the environment which gives us all the reason to act with caution. Hopefully, this blog post will help you understand the role of the coastal ocean on the global carbon cycle and the importance of preservation of balance within these environments. We have great impacts on the environment around us which gives us all the reason to act with caution.

Scientific term definitions are available.