What lives under the sea?

Hint: Not mermaids
Disappointed? Read on, because I think the answer is way more ornate and beautiful than a Disney caricature

Day or night, the music is always blasting in the wet lab where Debbie Steinberg (Virginia Institute of Marine Science) and her group are investigating zooplankton and other small organisms. At each station they deploy two different tow nets to collect organisms from the ocean, some at 120 m deep and others at 300 m deep. They slowly haul these nets through the water – so slow that bigger things like fish can easily swim away and avoid being caught. After hauling the nets on deck they spend many hours sorting through the various organisms that were caught.

Undergrad Jack Conroy (back) and grad student Tricia Thibodeau (forward) sort and identify the organisms from a tow.

They look at the types and quantities of organisms that live in the water. For two specific types of organisms, krill and salps, they also measure the length of each organism. Length then gives them a sense for the age distribution of the population, much as height would for humans.

Krill (Euphausia superba) being counted by lab guru Joe Cope

Observations of zooplankton have been going on in this region every year for many years. That might sound repetitive, but each year is different. For example, this year has more salps than they have seen before. This is important because it indicates larger changes in the environment. Salps prefer to live in open waters which are a bit warmer (not full of ice). Increasing average global temperatures include rising ocean temperatures – making the environment more hospitable for salps.

This is a salp (Salpa thompsoni). The orange-red blob is its “stomach” which is full of diatoms, a type of phytoplankton (the microscopic plants of the sea).

Alternatively, krill prefer to live in higher nutrient waters closer to the coast. Juvenile krill depend on algae embedded on sea ice to survive. Grad students Josh Stone and Tricia Thibodeau explained to me that as sea ice melts due to warming temperatures, there is less food for young krill. As a result the krill population diminishes. This starts a domino effect within the food web, because whales, penguins and seals all depend on krill as a vital food source.

An assortment of organisms from the tow, including larval fish and spongiobranchaea – a predatory sea slug!

Some polychaetes of the genus Tomopteris in a jar. These remind me a lot of centipedes, and are known to be voracious predators of other small marine organisms. They were swimming around their jar very quickly, wiggling their many legs and their long bodies. It was almost like they were dancing to the music!