Today I am heading ashore with Professor Juliet Brodie and Dr. Rob Mrowicki from the Natural History Museum in London
Juliet, Rob and Steve set up the shore transect. Credit: Claire Goodwin
Today I am heading ashore with Professor Juliet Brodie and Dr. Rob Mrowicki from the Natural History Museum in London. Juliet and Rob are our seaweed team. During the cruise they are sampling for their Darwin Plus Project "DPLUS122 - Biodiversity discovery and the future of South Georgia's seaweed habitats". Currently we know very little about the seaweeds present in South Georgia. Only 127 species have been listed as present – this is likely to be a major underestimate. Seaweeds are an important component of the island’s coastal biodiversity. Forests of giant kelp fringe many of South Georgia’s shores, many types of red, brown and green seaweeds live in the kelp’s shadows. Bedrock is often covered in bright pink encrusting coralline algae. Many of these seaweed species are at the edge of their distribution ranges and are likely to be affected as South Georgia’s seas warm. The information that Juliet and Rob collect on seaweeds will provide an important baseline for monitoring the South Georgia Marine Protected Area.
Our aim today is to revisit some transect sites last surveyed in 1991 to see if the seaweed diversity has changed. We are travelling to the beach in the zodiac. This small boat can get closer to the shore than the RHIB, the larger boat we use for diving. But unlike the RHIB we are not lowered into the water. We don floatation suits and climb down the pilot ladder. Then the crew run us ashore.
For shore work the seaweed team are run ashore in the zodiac. But first they must climb down the pilot ladder. Credit: Steve Brown
We’re halfway through the trip now so have got more used to the fur seals. The males are guarding their territories on the beach, waiting for the females to come onshore to breed. We are armed with broom handle ‘bodgers’ to fend them off if necessary. But we are much better at sensing the imaginary edges of their territories and staying out of their way than we were at the start of the trip. Luckily there are not too many near our transect site and the ones that are nearby seem more interested in napping than bothering us. Whale bones litter the top of the shore which are presumably remnants from the whaling station of Husvik which is across the bay. Our transect stretches from the whale bones to the lowest part of the shore. Juliet uses levelling sticks to position a quadrat at 20 cm height intervals down the beach. From each of these quadrats we record the percentage cover of the various seaweeds. We also collect samples of each so Juliet and Rob can identify these later. I have to concentrate to detach the tiny seaweeds from the rock with my tweezers so I am glad Steve is on fur seal look out duty. We have some young males who are trying to come on to the beach and our transect is in their way.
This fur seal isn’t too excited by our survey. Credit: Claire Goodwin
Claire helps Juliet remove seaweed samples from the quadrat. Credit: Steve Brown
When we get back to the ship, we carry the seaweed sample bags into the lab. This is a portacabin on the ship’s foredeck. It’s here that we process our animal and seaweed specimens. When I preserve my sponges, I just store them in ethanol but preserving seaweeds is a bit more time consuming. Juliet and Rob collect specimens themselves and are given bags full of seaweeds the rest of us have collected on dives. None of us are seaweed experts and often we collect multiple specimens of the same species. Next, the selected specimens must be pressed. Each is floated in seawater over a piece of acid free paper in a white tray. Juliet and Rob carefully arrange each specimen so that the identification features can be seen when it is pressed. A small piece of each weed is placed in silica gel to preserve it for genetic sequencing. The finished specimen sheet is placed between layers of newspaper and a non-stick fabric (gossamer) and multiple specimens are layered together in the presses. The aim is to dry out the specimens so they can be stored long term in the Natural History Museum collections. Each morning the newspaper must be changed for dry paper. Juliet has been getting ambitious and trying to press some of the large kelp specimens we have been collecting. Bosun Bob constructed a special metre-long press for her so she can preserve these giant specimens.
Rob presses seaweeds in the lab. Credit: Juliet Brodie
Some big seaweeds like the Himantothallus grandifolius are tricky to press. Credit: Juliet Brodie
All these specimens will make their way back to the Natural History Museum in London. Here the work will begin in earnest. Juliet and Rob will produce a seaweed identification guide and a checklist as a resource for other scientists. They also plan to develop a citizen science ‘Big Seaweed Search’ project that tourists visiting on cruise ships can participate in. I ask Juliet what she’s most enjoyed about the survey. ‘It was exciting to explore areas which have been studied so little previously. We were able to sample both the shore and subtidal, using divers. We’ve collected over 700 specimens and some of these will be new to science. Many are simply beautiful in their own right which makes the seaweed work a real pleasure’.