We are all bombarded by the growing campaigns to preserve our terrestrial forests, be it tropical to temperate. However, not far from our rocky shores, lurks a sub sea hub of activity, in the swaying fronds (algal leaves) of our kelp forests. Made famous by the Californian giant kelp, which can grow up to 45m in one growing season, kelp species of many sorts and sizes can imitate the complex habitat provided by a tropical rainforests and even coral reefs.
The physical structure of the kelps provides shelter and creates favourable conditions for the fauna and flora which has become reliant upon these properties. The different structural properties of kelps can be classified under three ‘guilds’; canopy, stipitate and prostrate.
Canopy: larger of the species which typically grow long surface reaching canopies.
Stipitate: shorter in height and grow on a rigid stipe (supporting stalk) to protect the vulnerable fronds from the benthos of a few metres in length but grow in thick fields on the sea floor.
Prostrate: also shorter than canopy species, grow in the shallows and tend to cover the sea floor with their fronds.
It is the co-existence of these guilds, and the many species which are classified by these structural terms, which create such diverse habitats for a diverse assemblage of inhabitants. It is not only the presence of variable niches for the creatures of a kelp forest, but the contrasting conditions they provide in an energetic coastal environment. Shading from the fronds allows favourable conditions for those benthic algal species that are adapted to low light to thrive. Dampening of the vigorous coastal currents allows for increased sedimentation and reduced erosion, which in turn impacts benthic productivity and recruitment of macrofauna.
Macrofauna associated with these forests have in some cases developed a reliance on this unique forest habitat. From limpets which have adapted to live in the cavities of the kelp stipe to the killer whales who hunt on the otters who forage in these slippery canopies.
We are now aware of the biodiversity these uniquely kelp driven ecosystems behold, but with the looming possibility that such species might be grown on a large-scale to provide our every energy need, it begs the question… can these man-made seaweed farms provide some habitat that may shelter and enhance local biodiversity?
As these cultured seaweeds will be hanging sub-surface structures they may not stimulate the benthic assemblages associated with classic kelp forests, but they can facilitate the pelagic macrofaunal species associated with such species, and may impact the benthos below in a similar manner to that of the anchored natural kelp beds. Even if these niches were to be exploited by local communities, kelp farms should take seriously the methods for harvesting and the timing if the benefits of these almost artificial reefs are to be reaped.
Just some more algal food for thought…