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…
Seaweed farms for biofuels may be coming to a Scottish sea loch near you soon, and although this idea is relatively new to most, the history of seaweed utilisation is deep-rooted.
Archaeological evidence suggests that Japanese aborigines ate seaweed as early as 300BC (Ragan and Bird, 1987), and in AD 701 it was written in the Law of Taiho that seaweeds -including kelp- were used to pay taxes to the courts! Now wouldn’t that be a nice thought in today’s economic crisis…
Closer to home, we are beginning to discuss and explore the reality of seaweed biomass for sustainable fuels of the future. However, historic remains in Scottish Bronze Age cremations suggest that even then, the anthropogenic uses of seaweed for fuel had been put to practise.
Currently, the kind of kelp farming we imagine as a resource of the future requires little in the way of 21st century technology, and the idea that kelp culture can be part of a larger scheme to utilise ‘Energy from the Sea’ is not a new one. Below is an article from 1975 in the magazine ‘Popular Science’ which describes an early trial by scientists and US Navy frogmen, who carried out a ‘mission’ to develop kelp culture 60miles out in the Pacific Ocean.
This idea, which at the time was quoted in the article as ‘far seeing’, is to date being explored by many international marine renewable research groups, and taking the next step towards the realisation of this once ‘far seeing’ idea is now coming to a head.
Here in the sea lochs of the Scottish west coast the Scottish Salmon Company have been trialling the co-culture of salmon and kelp to reuse the nutrient rich waste produced by fish farming. The potential to produce seaweed for fuel as a co-product of salmon cultivation is currently proving to be success, and is only paving the way for full-scale seaweed farms locally.
All-in-all from the historic to the futuristic, the realistic is fast approaching. It may have taken decades (if not more…) to refine that light-bulb moment of seaweed energy exploitation, and it could in our lifetime become part of the solution to the long anticipated fuel crisis.
Just another reason to become a fan of all things algae.
When we think ’emissions’ we think car exhausts and industrial cooling towers.Wrong. 20-30% of global emissions are a consequence of losses and degradation of natural ecosystems’ Trumper et. al.(2009).
CARBON COLOUR KEY
“Brown Carbon” Green house Gases (a gas which absorbs radiation and traps heat in the earth’s atmosphere, e.g. CO2)
“Black Carbon” The particles leftover from incomplete combustion of fossil fuels (soot and dust), which has a greater effect on radiation transmission. This in turn can directly and indirectly reduce the albedo effect of global snow and ice.
“Green Carbon” Carbon incorporated into plant biomass and the soils below.
and our friend…
“Blue Carbon“- carbon captured by the world’s ocean critters, and over half of all carbon in living organisms resides here, under the glassy and deceiving barren big blue. Important coastal vegetation habitats such as mangroves and seagrasses which acquire the carbon stored in marine sediments are being lost at a rate 5-10 times higher than the rainforests (Nellemann et. al. , 2009).
So what has this carbon rainbow got to do with seaweeds?… Well it has been noted in the ‘Blue Carbon’ UNEP Report that biofuels from land crops often replace natural and more efficient carbon capturing ecosystems (grasslands and forests), producing more CO2 than the replacement of fossil fuels.
Could seaweed culture for the production of biofuels be carried out on a large-scale without the degradation of what carbon capture was already going on? Could it possibly even enhance the carbon capturing ability of a local environment by increasing sedimentation and acting as an artificial habitat for creatures that call kelp home?…these are yet unanswered questions.However what is clear, is the ability of marine vegetation to naturally store CO2 which is being prematurely released into the atmosphere through ecosystem degredation.
So back to the blue carbon, unlike rainforests which store carbon for decades, the uptake of carbon by marine organisms (seaweed and seagrasses alike) can naturally lock up and store these green house gases for millions of years in seabed sediments, and have been doing so for the many years they have existed before us.
Just another reason to become a fan of all things algae. Blue Carbon.