Ocean researchers find biological clues in a bottle of seawater

A seawater sample can contain evidence of animals that a camera never captured. Organisms leave genetic material behind as they move through their environment, and researchers can analyse this environmental DNA to investigate marine biodiversity.

The approach is particularly useful in places that are difficult to observe directly. Filtering water concentrates biological traces for laboratory analysis. Researchers then compare genetic sequences with reference information to look for evidence of particular organisms or broader groups.

The result is not a simple underwater head count. Currents can move material away from its origin, DNA degrades, and a reference database may not include every species present. Collection and laboratory procedures also need controls to distinguish a genuine signal from contamination. An absent detection does not necessarily mean an animal was absent.

Environmental DNA therefore works best alongside observations, habitat information and other sampling methods. Repeated measurements can help reveal patterns that a single expedition might miss. Its value lies in adding another line of evidence to ocean surveys, especially where the cost and difficulty of exploration leave large gaps in knowledge.