Carbon sequestration processes and mechanisms in coastal mariculture environments in China

Dissolved organic carbon (DOC) release by seaweeds (marine macroalgae) is a critical component of the coastal ocean biogeochemical carbon cycle but is an aspect of seaweed carbon physiology that we know relatively little about. Seaweed‐derived DOC is found throughout coastal ecosystems and supports multiple food web linkages. Here, we discuss the mechanisms of DOC release by seaweeds and group them into passive (leakage, requires no energy) and active release (exudation, requires energy) with particular focus on the photosynthetic “overflow” hypothesis. The release of DOC from seaweeds was first studied in the 1960s, but subsequent studies use a range of units hindering evaluation: we convert published values to a common unit (μmol C · g DW−1 · h−1) allowing comparisons between seaweed phyla, functional groups, biogeographic region, and an assessment of the environmental regulation of DOC production. The range of DOC release rates by seaweeds from each phylum under ambient environmental conditions was 0–266.44 μmol C · g DW−1 · h−1 (Chlorophyta), 0–89.92 μmol C · g DW−1 · h−1 (Ochrophyta), and 0–41.28 μmol C · g DW−1· h−1 (Rhodophyta). DOC release rates increased under environmental factors such as desiccation, high irradiance, non‐optimal temperatures, altered salinity, and elevated dissolved carbon dioxide (CO2) concentrations. Importantly, DOC release was highest by seaweeds that were desiccated (<90 times greater DOC release compared to ambient). We discuss the impact of future ocean scenarios (ocean acidification, seawater warming, altered irradiance) on DOC release rates by seaweeds, the role of seaweed‐derived DOC in carbon sequestration models, and how they inform future research directions.

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“…(2010) and Zhang et al. (2017). DOC is produced in the euphotic zone (0–100 m) via photosynthesis and subsequent food web interactions.…”

Section: Biogeochemistry and Fate Of Doc In The Marine Environmentmentioning

confidence: 97%

Rate and fate of dissolved organic carbon release by seaweeds: A missing link in the coastal ocean carbon cycle

Paine

Schmid

Boyd

et al. 2021

Journal of Phycology

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“…While seaweed sequestration potential may be high in many regions, the global reduction of carbon emissions, especially to stay below 2 C, still rests on cleaner sources of energy and protection of our expansive, but threatened, carbon sinks, including wild blue carbon biogenic regions [30]. However, targeted industrial-scale expansion of seaweed offset farms in regions, such as Asia-where potential is high, farming already occurs ( Figure 1), and mariculture sequestration is gaining interest (e.g., [31])-could help make substantial strides toward these ambitious goals as well as provide other local ecosystem services [7,8].…”

Section: Resultsmentioning

confidence: 99%

Blue Growth Potential to Mitigate Climate Change through Seaweed Offsetting

et al. 2019

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“…Additionally, in the groups containing algae, the DOC content significantly increased. The DOC makes up a portion of organic carbon that is effectively sequestered as it enters food webs via the action of microfood loops or forms inert organic carbon and stays in the sea for a long time [42,43]. According to Jiao [44], microbial carbon sequestration as a carbon sink is often overlooked, and the core mechanism of microbial carbon sequestration is its conversion of DOC into refractory DOC (RDOC) that is stored in seawater for extended periods.…”

Section: Discussionmentioning

confidence: 99%

Experimental Study of the Environmental Effects of Summertime Cocultures of Seaweed Gracilaria lemaneiformis (Rhodophyta) and Japanese Scallop Patinopecten yessoensis in Sanggou Bay, China

Liu

Wang

et al. 2021

Fishes

Self Cite

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The shellfish–algae mode of integrated multitrophic aquaculture (IMTA) is a sustainable aquaculture method that benefits the environment and the carbon cycle. However, most current shellfish–algae aquaculture modes are based on the expansion of kelp aquaculture. Due to the low tolerance of kelp to high temperatures, integrated shellfish–algae aquaculture areas often become shellfish monocultures in summer, which may lead to both high mortality rate of shellfish and to economic loss while causing serious environmental harm via eutrophication, decreases in dissolved oxygen (DO), and decreases in pH. In this study, we investigated the effects of different ratios of seaweed (Gracilaria lemaneiformis), which is tolerant of high temperatures, to Japanese scallop (Patinopecten yessoensis) on water quality and environmental parameters. A two-day small-scale enclosure water body experiment was conducted in Sanggou Bay (Shandong, China) in August 2019. The results demonstrated that culturing shellfish alone significantly affected pH, DO, eutrophication, and other environmental indicators, as well as the carbonate system. The negative environmental impact of the shellfish–algae aquaculture system was much smaller. However, too high a proportion of algae might consume excessive amounts of dissolved inorganic nitrogen (DIN) and nutrients, while too low a proportion of algae might not fully absorb the nutrients released by the cultured shellfish, in turn leading to an increased risk of eutrophication. The shellfish–algae aquaculture system not only improved the inorganic carbon system, but also the organic carbon system. At the end of the experiment, all the parameters of the inorganic carbon system had decreased significantly, while all the parameters of the organic carbon system had increased significantly. The results of this study illustrate the need to include macroalgae rotations in summer, and that an appropriate ratio of shellfish to algae is necessary to achieve a sustainable aquaculture system. Moreover, this research has also confirmed the importance of the future and related research in the actual production, which will provide useful information to guide governmental strategies for summer aquaculture rotations and insight into the controversy concerning whether aquaculture is a carbon source or sink.

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Carbon sequestration processes and mechanisms in coastal mariculture environments in China

Cited by 67 publications

References 38 publications

Rate and fate of dissolved organic carbon release by seaweeds: A missing link in the coastal ocean carbon cycle

Rate and fate of dissolved organic carbon release by seaweeds: A missing link in the coastal ocean carbon cycle

Blue Growth Potential to Mitigate Climate Change through Seaweed Offsetting

Experimental Study of the Environmental Effects of Summertime Cocultures of Seaweed Gracilaria lemaneiformis (Rhodophyta) and Japanese Scallop Patinopecten yessoensis in Sanggou Bay, China

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