Spring in the sea

Spring in the sea

Aeolida filomena eggs - Allan Rowat

Nia Jones (Living Seas Manager) describes some of the events in a typical marine spring.

We all love to see the Spring “springing” and whilst we welcome the return of some of our most well-known creatures on land spare a thought for some of the unseen Spring spectacles happening in our seas.


this increase in food availability during Spring and early Summer means that we also start to welcome the arrival of migratory species

At this time of year a number of creatures are breeding, ready to release eggs and larvae in time for the plentiful food that will be available during the Spring plankton blooms. Plankton, derived from the Greek word “planktos” meaning wanderer, are drifting organisms often only visible with a microscope. Some types – the phytoplankton - photosynthesise and so the increase in availability of light as the days get longer and warmer causes a bloom. As a result we see an increase in larval and animal plankton – the zooplankton, which eat the phytoplankton. This is the basis of most food chains in the marine environment and so this increase in food availability during Spring and early Summer means that we also start to welcome the arrival of migratory species such as basking sharks, mackerel and several species of seabirds into the Irish Sea.


On the sea floor, dead man’s fingers, a type of soft coral, will be shedding the outer “skin” along with anything that may have settled on them during the Winter months. The tentacles are then ready to extend to feed again. Annual seaweeds will have started appearing whilst those perennial in nature will start their Spring time growth.


You may start noticing translucent gelatinous balls known as sea gooseberries with their two trailing tentacles, stranded on the beach or in rockpools. Look carefully and you may see the iridescent ripple of the “combs”. Next to arrive, towards the end of Spring, will be ghostly blooms of jellyfish - several species can be seen in Welsh waters.


Closer to shore, our rockpools are hosting Spring for creatures like sea slugs. Sea hares, so called after their tentacles that resemble a pair of hare ears, can be spotted as they come to shallower waters to breed and lay their long pink egg strings at this time of year. The largest and most common is the sea lemon with its rosette egg ribbon that can be easily seen on the lower shore. Sea slugs, unlike their land-based counterparts, are indeed some of the prettiest creatures in the sea. They look their best in water, so take time to just watch life in the rockpool next time you're out. Take care to keep all life safe by keeping to the rockpooling code.


Although mostly an unseen phenomenon, springtime in the sea is a hive of activity and excitement just like on land. You can keep up with marine news on the Living Seas Wales website and we're also on Facebook, Twitter and Instagram.