Linnea Bergdahl, Länsstyrelsen, 11 May 2018
An algae, a pet, a home decoration, a companion in the fish tank – the moss ball (Aegagropila linnaei) may be described in many different ways. And it can be found right here in the northern Bothnian Bay.
This peculiar looking algae may also be called marimo, which is a japanese word that literally translates to “ball seaweed”. The moss balls are no alien eggs but rather a specie of filamentous green algae (Cladophora) that grows into the shape of round balls. They may be found in lakes in for example Iceland, Scotland and Japan. Today they have become popular in fish tanks and you can order your very own moss ball online if you’d like to have one at home.
During inventories within the SEAmBOTH project area, divers have found the moss balls at deeper bottoms constisting of hard surfaces such as rocks and stones. It is difficult for other plants to grow in the deeper, darker waters on hard surfaces where they have difficulties attaching themselves to the bottom. The moss ball on the other hand favours these conditions and is often the dominating specie in these areas.
All the small green plants in this photo are Crassula aquatica. (Photo by Suvi Saarnio, Metsähallitus)
Special species
Indicators
Essi Keskinen, Metsähallitus, 23 November 2018
Indicator species means a species which tells something important about its environment or the environmental conditions where it thrives. Bladder wrack Fucus vesic-ulosus deteriorates in turbid water and the plants move towards the surface to catch more light, blue mussels need at least 4-5 per mill salinity to survive, and Vauche-ria sp filamentous algae grow well in eutrophicated sheltered areas.
Water framework directive WFD aims to good ecological water quality and one of the indicators in Finland is the bladder wrack. It’s depth zone is monitored, and it seems to correlate quite well with water turbidity (or the lack of it), which correlates quite well with the amount of plank-tonic algae in the water column, which correlates quite well with the nutrient load in the water, which correlates quite well with the water quality. But there’s always a But. Bladder wrack depth preference doesn’t really correlate that well with anything in the Archipelago Sea.
The reasons are not well understood, but in this area, the species is not as strong an indicator as elsewhere. And another But: Bladder wrack doesn’t exist in the Bothnian Bay and in the SEAmBOTH area at all so we can’t use that species to indicate anything, besides the lack of it indicating too low salinity for its growth.
It’s been a long and rocky road looking for environmental indicator species in the Bothnian Bay. One Master’s The-sis (Takalo, 2005) came to the conclusion that the vas-cular plants are not very useful indicators (of anything) in the Northern Bothnian Bay because of the special environmental and geographical circumstances (constant and fast land-uplift, abundance of river water, long ice cover and the low number of vascular plant species due to the aforementioned facts). Takalo does mention that epiphytic algae or Diatoms might be used as indicators of eutrophication. Another Master’s Thesis (Lantto, 2016) looked into the possibility of using filamentous algae
to indicate eutrophication in the Northern Baltic Sea.
Lantto did find a correlation between the two, but warns us not to interpret the correlation too lightly – it could be caused by other environmental factors (for example temperature) and not eutrophication alone. Diatoms form a large biomass in the Northern Bothnian Bay, but study-ing them requires special identification skills and special microscopes and hasn’t been studied yet.
One thing we can say for sure: there are some species even in the SEAmBOTH area that indicate something.
Nitella wahlenbergiana most definitely indicates a river estuary, while Crassula aquatica indicates a mud flat or some other very shallow area where water level fluctu-ates, and Chara aspera might indicate a sand bank. What is still problematic with these indicator relationships is that for example Chara aspera might also grow in other environments as well, and for example Potamogeton frie-sii seems to prefer two very opposite habitats – muddy and sheltered black water ponds with soft bottom on the other hand, and clear water pebbly or sandy bottom, quite exposed areas in the outer archipelago on the other.
Trying to make indicator species out of any species is like trying to categorize every patch of nature into nature types. All of them just don’t fit in to the special little niches we try to push them into. Regardless of the diffi-culty of categorizing them, the species will keep growing and leave us wondering what they tell us about their surrounding nature, if anything.
Vaucheria covering the bottom, giving it a green “fur”. (Photo by Petra Pohjola, County Administrative Board of Norrbotten)
Vaucheria
Petra Pohjola, Länsstyrelsen, 14 December 2018
Filamentous algae are those thin fussy-looking, some-times slimy, algae may find growing on hard substrates where they cover rocks and stones.
Some of them though grow on soft bottoms. Examples of these algae that specialize in growing on soft sed-iments are species of the genus Vaucheria. Vaucheria are yellow-green algae that grow long, tube formed and unbranched filaments that often can be seen growing straight up from the soft sea bottom like green spiky hair.
In some places the algae grow so abundantly that it looks like a green mat covering the whole sea floor.
There gas can accumulate underneath the dense vegeta-tion, forming gas pillars in the Vaucheria-mat, as seen in the video.
The video is taken during a free dive to a depth of about 2,5m, in a shallow bay where the bottom at the deepest part was covered by these algae.
Canadian waterweed is bright green in color and has tongue-formed leaves. (Photo by Petra Pohjola, County Administrative Board of Norrbotten)