Last week I went for a little swim at the usual spot at Castle Beach. The viz was nowhere near as good as last month, but still OK. There are schools of sand eels and sand smelt and I even saw an eel. The contrast between growing brown seaweeds and withering red seaweeds has become even greater. Below you see some yellowed Harpoonweed and a ‘forest’ of Thong weed covered in epiphytes. As the light was a bit subdued, I focused on the most shallow area. The bare parts of the rock are covered with barnacles, dog whelks, sting winkles and limpets. The seaweeds are mainly Serrated wrack Fucus serratus, Sea lettuce Ulva, Grape pip weed Mastocarpus stellatus, some Ceramium and Laver Palmaria palmata, as well as Dumont’s tubular weed Dumontia contorta.
It is my plan to post photos of seaweeds from one large rock pool in Falmouth every month. As I am making good on my new year’s resolution of going out to the beach, I have some more photos to post before it is February though. I am slowly learning to take better photos, but will also post ones that are not that great to cover more species. Below, Club bead- or Feathery tube weed Lomentaria clavellosa, the small epiphyte Little fat sausage weed Champia parvula (heavily cropped, I need a macro lens!) and Juicy whorl weed Chylocladia verticillata (with some of the edible Dulse Palmaria palmata on the left of it).I found quite a few more species but the photos ended up a bit meh, so I will have to go back and try harder. Below, two that ended up quite nice. Serrated wrack Fucus serratus covered with a variety of red epiphytes and a piece of washed up Sea oak Halidrys siliquosa.
When going out rock pooling, I always take my iPhone and Canon Powershot (for underwater use) and take at least a couple of photos. Because of a lack of time, or because a single good photo is not enough for a new post, not everything ends up on the blog. Now I have some free time, I picked a couple of unused photos made this year that seem blog-worthy. First up, In realized only what I had found on the beach at St. Ives when leafing through the The Essential Guide to Beachcombing and the Strandline: a Seabeard! This hydroid, Nemertesia antennina, grows as stiff colonies protruding from a matted base and occasionally washes up on shore. It looks a bit plant-like; at the time I did not have the opportunity to have a closer look and just snapped a quick photo. Next a Lesser sandeel Ammodytes tobianus found at Gylly beach. I always see them when snorkeling or diving (see here) but this was a good opportunity to see one up close (I get excited when I spot a dead fish on the beach (see also here) and I am not afraid to admit it!). Following are two colour varieties of the Spiny starfish Marthasterias glacialis, a Common brittlestar Ophiothrix fragilis and a shot of an Aequorea forskalea (or maybe A. vitrina) jellyfish. Next the gastropod mollusc Chinaman’s hat Calyptraea chinensis. I went back to Mylor marina for some pontooning recently but not much was growing; the only thing that stood out was the luxuriant sponge growth (I am not sure of the species, perhaps Halichondria).And of course some seaweed pictures. By iPhone: Under tongue weed Hypoglossum hypoglossoides in Flushing, Black scour weed Ahnfeltia plicata in St. Agnes and a photo showing a variety of wracks all colonizing the same patch (Flushing): Serrated wrack Fucus serratus, Spiraled wrack Fucus spiralis, Bladderwrack Fucus vesiculosis and Egg wrack Ascophylum nodosum. Next some Canon Powershot underwater pics (see also this post and this one): a random rock pool picture of mostly decaying seaweed, a closeup of my favourite the Bushy rainbow wrack Cystoseira tamariscifolia and a shot of Wireweed Sargassum muticum that has completely taken over a pool. Finally an SLR photo of a rock pool at Gylly beach with large Cystoseira baccata plants (middle, Wireweed on the left).
Time for the second post on the topic of seaweeds in the aquarium and I will write a part III as well.
4. What conditions are right for seaweeds?
The short answer is: I don’t know yet (and they will vary for different species). I have some clues that add up to a longer answer though. Obviously light is an important factor. Most tanks come with actinic (blueish) light representative of deeper waters. The seaweeds I collect are from shallow water (rock pools) and so are adapted to whiter daylight (as in freshwater planted tanks). I have played around with lighting (see this post) but not in a very systematic way and so am not too sure about what wavelength and intensity is best. Another factor that is important is sufficient wave action. Before I used a Tunze nanostream to create extra flow, I noticed that detritus and algae could settle on seaweeds, see this picture of Serrated wrack Fucus serratus taken from an older post:
High nutrient levels could benefit some microalgae more than they benefit macroalgae (seaweeds) as is the case for plants in fresh water aquariums and could lead to problems. Another factor that must be very important is temperature. I do not have a chiller and my tank is around 25C (higher than room temperature because of the lighting). Seaweeds from rock pools must have not much problems tolerating this temperature for hours on end, but many might have a problem with it for months on end. I therefore will probably buy a chiller next year… One very interesting parameter that I have not yet seriously considered is CO2. CO2 can be a limiting factor in photosynthesis, that is why many fresh water aquarium keepers add it (in gas or liquid form) to promote plant growth. I found a very interesting article on the role of CO2 in reef aquariums by a very clever chemist named Randy Holmes-Farley. It could be that CO2 is limiting for seaweeds in my aquarium as well and I’ll definitely need to do some pH tests to find out whether this could be the case. The article lists a table with relative rates of photosynthesis at pH 8.7 compared to pH 8.1 for a number of seaweeds. This is 57% for my favorite seaweed Bushy rainbow wrack Cystoseira tamariscifolia. Very interesting stuff indeed and I shall investigate!
Last Sunday I ventured to the north coast for a rock pool ramble with Matt Slater of the Cornwall Wildlife Trust (see this great blog) and the local marine conservation group (who also have a nice blog). I actually had never rock pooled at the north coast before (shame on me) and so it was nice to see this exposed habitat, quite different from my main haunts at Castle Beach in Falmouth and Trefusis Point in Flushing:
The rocks were much more bare and the number of animals a lot lower. However, there were quite some seaweeds. I finally saw (the edible) Laver Porphyra spp (probably Black laver Porphyra dioica):
Another edible species, Dulse Palmaria palmata, was incredibly common here:
I won’t add too many seaweed pics in this post, but I liked this shot of Serrated wrack Fucus serratus:
Brown and yellow Flat periwinkles Littorina obtusata (or possibly Littorina mariae, I did not bother to check) where common:
We found a Shore cling fish Lepadogaster lepadogaster and a Five-bearded rockling Ciliata mustela:
I found a couple of pieces of a branched seaweed covered in the bryozoan Electra pilosa:
All in all a good session. I hope to go back soon to take better pictures of the seaweeds!
I am not sure if I like the term aquascaping much because of it’s connotations with gardening and I like a more natural look. However, aquascaping is the general term for arranging plants in an aquarium nowadays and that is what I attempt to do as well with seaweeds. (Also, I cannot pretend that my tank looks particularly like a real rock pool…). Anyway, I will post some more thoughts on the topic of aquascaping, marine or fresh water, later but for now just wanted to show some of the first attempts at planting my aquarium, It is challenging to make any tank look ‘right’, but I found it particularly hard to recreate a rock pool feel. I soon found out that I did not have enough rock in the tank and so hauled some *heavy* ones from a nearby beach. The bare tank:
Another version with Serrated wrack Fucus serratus (left), a small mop of Dudresnay’s whorled weed Dudresnaya vertillicata (far left) and some Solier’s red string weed Soliera chordalis (middle and right). A bit messy:
A worm pipefish, dog whelk and hermit crab in front of the serrated wrack. There is a lot of algal growth and detritus on the wrack. (I have since bought a circulation pump to keep detritus in suspension so it can go into the filter, more about that later).Another go. The nice thing about having an aquarium with native species is that you can collect them yourself, which is half the fun (and free), and when something does not work out you just chuck it back and try something else. The green seaweed is velvet horn Codium tomentosum, the long brown seaweed is wireweed Sargassum muticum. Both did well, the wireweed grew quite fast, perhaps not a surprise as it is an invasive species in the UK. The red seaweed on the left is dulse Palmaria palmata, on the right harpoonweed Asparagopsis armata. The harpoonweed was not exactly thriving and the dulse was quickly eaten by the prawns:Recently, I noticed the Dudresnay’s whorled weed (love that name) sprouting from the rocks everywhere. This happened some months after removing a pluck of this weed from the aquarium. Up till then I had just planted seaweeds, but having them establish spontaneously I had not seen before. Most of the newly established weeds are only a couple of centimeters and do not seem to grow very fast, but the two weeds pictured above grew to 10 centimeters in a couple of weeks. Perhaps very local conditions in the aquarium matter.