APEM Aporrhais pespelicani being weighed

A sample of Aporrhais pespelicani being weighed

The marine environment encompasses 70% of the earth’s surface and is responsible for about half of its total primary production of energy by living organisms including plants.

Global expeditions and increasingly better sample techniques have improved our ability to make quantitative observations of marine organisms and increase our knowledge on taxonomic and distribution patterns.

Biomass is defined by the weight of an animal or plant species. It is a continuous quantity that can be useful for general and community assessment. Body size is a characteristic that determines basic life processes of organisms such as metabolic rate and movement speed.

In the marine environment, biomass is dominated by three kingdoms – animals, protists (non-photosynthetic and photosynthetic unicellular eukaryotes) and bacteria. In contrast to their domination on land, plants account for less than 10% of total marine biomass. Marine animals are mainly dominated by fish and crustaceans such as shrimps and krill.

In a marine community, body size can determine species interactions including their position in the food chain. Knowledge of body structure of a community can be a descriptor but also a possible indicator of environmental changes. Studies[1] have shown that less impacted aquatic environments had higher biomass values than perturbed ones.

Aporrhais pespelicani (Pelican’s foot) drying for biomass

Aporrhais pespelicani (Pelican’s foot) drying for biomass

Biomass can be determined in a variety of ways – dry weight, wet weight and ash free dry weight. When biomassing animals, wet weight is the preferred method as the other methods would destroy them and preclude any subsequent reference or quality control checks.

The wet weight is obtained by weighing animals after external liquid has been removed on blotting paper. The animals are placed on absorbent paper and moved around until no wet traces are left behind. Tube dwelling animals are removed from their tubes before weighing, while animals with shells are weighed with their shells. As soon as they are blotted dry, animals are transferred to a tared dish on a scale and measured in grammes to 4 decimal places. It is important to use an annually serviced, calibrated analytical balance to gather these data, especially as macrobenthic invertebrate biomass by taxon often involves values of less than 0.0010 g. Biomass values should always be qualified with analyst and equipment data. Procedural guidelines for the biomass of macrobenthic samples are provided by the Northeast Atlantic Marine Biological Analytical Quality Assurance (NMBAQC) scheme.

Gaining a comprehensive, quantitative knowledge of the current state of a community biomass is becoming progressively more important with the increased anthropogenic pressures on marine ecosystems.

APEM’s marine BioLabs has several years of experience biomassing organisms from different habitats from all over the world.

[1] Machuca-Sepúlveda, J., Fierro, P. & Nimptsch, J. Variability of benthic macroinvertebrate biomass in two contrasting streams in southern Chile. Hydrobiologia 849641–660 (2022). https://doi.org/10.1007/s10750-021-04731-6

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