Benthic Ecology

Researchers sort and identify animals

Researchers sort and identify

Ecology is the study of living things and their environment. 'Benthic' means bottom or seafloor. Therefore, 'Benthic ecology' is the study of living things on the seafloor and how they interact with their environment. The benthic ecology team at Geoscience Australia studies the animals and plants on the seafloor and how they relate to each other and to their environment. The two main survey techniques for benthic ecology are biological sampling and use of photography and video.

Ecologists at Geoscience Australia work in the field collecting samples and in the laboratory sorting and identifying animals. In the office the team analyses the data to contribute to deriving national biodiversity datasets and mapping patterns from the continental shelf and slope as well as focusing on discrete study areas along the coast.

Biodiversity refers to the number and types of organisms in a region. It is measured in different ways:

  • number of individuals (population size, abundance)
  • number of species (species richness)
  • diversity indices (can include both population size and species richness)

Although improved methods and technologies have facilitated seafloor sampling, it is still very difficult to collect and identify marine animals and plants, particularly in the deep sea. The fact that Australia has one of the three largerst marine jurisdictions in the world, makes it practically impossible to catalogue all of the marine life using direct sampling techniques. Another way is needed to predict Australia's benthic diversity.

The team at Geoscience Australia is trying to identify physical factors that are easier and faster to measure so that they can be used as predictors of benthic marine biodiversity. Surrogates may include temperature, depth and the mud content of the seafloor.

Retrieving a biological grab from the seafloor

Retrieving a biological grab from
the seafloor

Ecologists can collect animals which live on the seafloor by using equipment such as sleds and dredges. Animals that live in the sediment are collected using grabs and various types of cores (e.g. boxcore). Finally, benthic animals can be directly observed in their environment using underwater video and photography. Once a sample is collected, the animals are preserved, sorted in the laboratory, and subsequently identified.

Animals and plants that live on, in or immediately above the seafloor are collected from shallow bays, continental shelves and slopes and abyssal plains. Many of the animals photographed and/or collected are familiar, such as fish, starfish and crabs. Other animals look more like exotic colourful plants, such as sponges, gorgonians and the various animals that live on their surfaces. Many animals are tiny particularly in the deep sea. These animals can have amazing features such as double-jawed worms, camouflaged crustaceans or glass-latticed sponges, and have to be identified and described under a microscope.