Science in restricted territory

Dec 11-15
Sometimes, when people find out that I’m a scientist, they ask: “So, what have you discovered?” Usually, I’m at somewhat of a loss to answer this question. It’s not easy to compress the fine details of interaction strengths in a food web into a comment that is both intelligible and compelling. Or I sound vague and undecided in stating – truthfully – that one species can have both positive and negative effects on another, depending on time, place, and what is being measured. Now, however, there’s a clear answer for the “discovery” question: Alan and I discovered a new species, which has never been reported from Africa, but which has strong negative effects on bivalves. Furthermore, there is good evidence that the species is not a new introduction, but simply something that no one bothered to record previously. This ease of discovery is the silver lining of sabbatical in a country where you can count the marine biologists on one hand.

The species we discovered is a phoronid worm that burrows into shell. Phoronids are unsegmented worms, currently included in the same phylum as brachiopods, with which they share a horseshoe-shaped ring of tentacles for filter-feeding. Phoronis ovalis is the only phoronid reported to burrow in shell, and the other dozen or so species of phoronids make free-standing tubes. Very little published literature is available on Phoronis ovalis, but by piecing together papers and websites, it appears to have a temperate distribution that includes Scandinavia, the Mediterranean, Pacific Northwest, New Zealand, east and west coasts of South America, and Japan. It has not been reported anywhere in Africa, including South Africa (where its absence may be genuine, since there is close scientific attention to marine species). But it’s definitely in Namibia. Here are some things we’ve learned about it (let’s call it Phoronis sp., since we can’t be sure it’s P. ovalis): The ring of tentacles is less than 200 microns across, and the total worm length is around 2 mm. The burrows come to the surface at densities of more than 100 per square cm. Shells that are seriously infested with phoronids become porous but thicker, because the host has to repair and re-apply shell on the inside. This takes so much energy that the host itself loses condition! Phoronids are not too picky about host species, as long as they are essentially always under water: we have found phoronid holes in Perna perna (brown mussel, our main study species), Choromytilus (native blue-black mussel), Mytilus galloprovincialis (introduced blue-black mussel), limpets, whelks, and even a barnacle. How could this species have gone unnoticed for so long? More than half the mussel shells on the beach are riddled with these holes! Maybe the answer is best summed up by the comment after our public talk at the Swakopmund aquarium in late November: The only mussel we’re really interested in is the “white mussel”, which scientists call a clam, and then only because we use it for fishing bait.

Well, to quote Dr Seuss again, “If you want to find beasts you don’t see everyday/ You have to go places quite out of the way./ You have to go places no others can get to./ You have to get cold and you have to get wet too.” Ever since we arrived in Namibia, we’ve wanted to see the full range of intertidal sites, but we’ve been limited to the area around Swakopmund because only this 200-km stretch of coast is publicly accessible. To the south, the coast is well protected by the great sand sea, and off limits to all but diamond miners. To the north, most of the Skeleton Coast Park is closed to public access. However, our discovery of Phoronis sp. in Namibia gave us a logical reason to face the administrative hoops and request a permit for beach access in the Skeleton Coast Park. (We have, alas, run out of time for southern sampling, but we have contacts in a few key coastal towns who may be able to report on the presence or absence of phoronid holes there.) After a few false leads, we finally had an in-person meeting with the Director of Parks and Wildlife Management, where we presented our case in a 2-page letter and – Eureka! – walked out with a Skeleton Coast Park permit! We were on our way into restricted territory with no roads, no people, but full of stories and legends to fuel our excitement!

The Skeleton Coast gathered its name and fame from a book by that name, written in the 1950s about events during WWII: a passenger ship ran aground at a point even farther north than our planned sampling, and rescues were attempted by land, sea, and air. Planes crashed, tugs grounded, trucks floundered in sand, but ultimately all but two of hundreds of people involved in the accident and rescue survived. By sea, the Namibian coast is nearly straight, with little in the way of protected harbors, and waves on shore that are large even in calm seas. The Namib desert is essentially devoid of freshwater, a forbidding barrier by land. The desert is breached at intervals by rivers, but these are generally dry, running to the coast only when inland rains are extreme, which happens every couple of decades. Mindful of the difficulties of negotiating such an area, we traveled with Mr Klein, our host at the Salt Company, who knew the coast by air and land from many years of prospecting and mining; we also traveled with one of our students from the Polytechnic, Uapindi Kazahe, who knows people wherever he goes. From Swakopmund (22.6 degrees S), we traveled north about 160 km to a campsite at Mile 108, then a further 200 km to Mowe Bay, where we camped for two nights at the end of the road. From there, on a day trip, we all got into Mr Klein’s Toyota Fortuner, which can ford rivers of sand, climb mountains, and stick to seaside cobble. We followed a track or the beach to our northern sampling site at Rocky Point (19 degrees S). On the return trip to the south, we camped at Torra Bay, totally outclassed by the summer holiday fishers who set up colorful castles of tents, windscreens, and caravans, with all the comforts of home powered by generators. We crossed the dry river mouths (in order from the south) of the Ugab, formed by Paleozoic glaciers; Huab; Koigab; the five mouths of the Uniab, including its current channel harboring reeds, gemsbok, and springbok; Hoanib, with a flamingoed lagoon bordered by a thick layer of snail egg cases; and avoided the quicksand that sometimes marks the mouth of the Hoarusib. Mr Klein had been stopped for weeks by these rivers in other years, so we were thankful for just minimal amounts of rain. (Actually, the weather was remarkably cooperative, particularly the absence of strong southwesterlies that can blow away campers, and rain just as we were packing to leave Mowe Bay).

What does a beach look like when human impacts are really low? The sand was littered with wood and whalebones. Vertebrae like coffee tables. Two-story ribs. The tough part of the back of the skull. A midden of charcoal and mussel shells, along with a ring of rocks, still was visible where native people had homesteaded perhaps a century ago, living in a hut of skins draped on whale ribs. We saw bits of old wooden fishing boats, the crashed airplane, and the top of the tug, swept by waves, along with several other wrecks. We saw the detritus of old mining operations, cleared areas where people had camped, piles of sand and stone, and rusty equipment for sorting beach gravel by size and density. Mr Klein said that Namibia’s large diamond mining company, Namdeb, sold its mining rights quite some time ago, which should have been an indication that prospecting on the Skeleton Coast was fruitless, but nevertheless some mining still goes on.

Most of the Skeleton Coast, and in fact Namibia’s coast in general, is sandy beach. Any species requiring hard substrate is restricted to a few outcrops (although what happens below low tide is something of a mystery: there must be rocks that we can’t see in some places, as indicated by kelp blades at the surface of the water). At the rocky sites we visited along the Skeleton Coast, the limpets and snails reached absolutely enormous sizes – 10 cm diameter, as big as a hand! Some familiar species disappeared: lobster molts and clam shells were not on the beach after Mile 108. New species amazed us: Ghost crabs popped out of their sand burrows by the hundreds and scattered across the beach. 1-cm moon snails with a comma umbilicus showed up on a few beaches and in jewelry for sale at the park entrance, but the comma necklace snail distribution is supposed to end at the southern tip of the continent. To the north, mussels became both smaller and less abundant, and some of the larger individuals were actually drilled – something we’d only seen in small clams and mussels in the Swakopmund area. Of course, we can’t know for certain how much of the variation in intertidal community structure that we witnessed on our trip was due to latitude, and how much to human access. The rock type varied as well: Rocky Point is made of rare red volcanic rock that only reaches the coast in one place. Other sites we sampled were a conglomerate, often eroded into steep intertidal mesas. At still others, layers of rock were turned on end. Most of the sites had been previously sampled by Spanish researchers, and the algal results reported in a monograph by Rull Lluch. But Alan’s extensive searching with Google Earth revealed one more rocky site, north of Terrace Bay in the restricted park area. It was particularly limpet-y, sort of like the bottom of a pink-red non-slip shoe, with lots of grippy bumps. The red and pink came from the apparently unpalatable algae, the bumps from the shells of limpets. Only where the cobble had recently receded could any green be seen on the rocks, more clear evidence of the importance of herbivores in regulating community structure, because the algae colonize these rocks faster than the limpets.

So what’s the story on phoronids? As we sampled north from Swakopmund, the prevalence first increased in mussels, and then as large mussels became less common on the beach, the frequency of phoronid holes also decreased. By the time we reached Rocky Point, we didn’t find any mussels with phoronid holes, although they showed up in a few snail shells. When we discussed our trip with Dr Bronwen Currie at NATMIRC in Swakopmund, she produced some large Perna shells that she had brought back from a rocky site near the Kunene River, the border with Angola: 1 of 10 had phoronid holes! And the marine biologists in South Africa are now sending photographs of snails with small holes in the shell: these may be phoronids, too! So it seems we haven’t quite finalized the entire range of the species, but we’ve found a 200-km stretch of coast where they are particularly common. We also found them buried in layers under about 3 m of silt, sand, and vegetation, now being eroded by waves at the base of a cliff – surely these must be quite old! But we are always warned that a 1-year snapshot of life on the beach is deceiving. That sand could have been deposited just a short while ago during a massive east wind blow. Like any proper “discovery”, ours still has a few mysteries remaining.

A change in the weather (and some more food comments)

Latitudinally, much of Namibia is tropical – we’ve passed the Tropic of Capricorn on a few trips to the south. Still, we’ve definitely experienced seasonal changes. In 2008, the summer rainy season was shifted later than normal, beginning in late-January and lasting until May. We personally experienced these late rains around 7 May at Swakopmund and 26 May at Etosha. Flamingos breed in the Etosha “pan”, a large saline body of water whose level fluctuates dramatically with precipitation and evaporation. The literature indicates that flamingos leave the coast in December to breed and return in April. This year, we watched flocks of honking pink birds fly north from Walvis Bay and the Saltworks in March, tracking the late start of the rains. They were inland until at least September, but probably didn’t breed successfully, as the pan had too much water: flamingos need a stable level so they can build mud nests rising out of the water, providing some protection from water-wary predators. The late rains were nonetheless torrential, and the northern part of the country flooded, resulting in poor crop production and emergency food deliveries.

By mid-April in Namibia, a sense of sadness is pervasive as the landscape changes from vibrant lush green to its drier hues. Stipagrostis bushmens grass has long nodding seed heads with feathery plumes, so abundant that the landscape turns silver, and the plumes accumulate before the wind in piles like small snowdrifts. Many of the desert plants seem not to be tied to the duration of the rainy season. They germinate with rain; they complete their life cycle with fog; and they fruit and dry up. So the landscape changed color even before the rainy season ended this year. Still, there were enough plants still flowering in May to keep JR’s parents busy with species identification while they visited!

Some of the plants that grow during the rainy season were worth sampling – given the history of hunter-gatherer societies in this region, we know there must be things to eat (in addition to the spiny, toxic ones that have evolved means of protecting their hard-won growth against herbivory). We saw fields of wild watermelons throughout the country, from the highlands around Windhoek to the wild lands of Etosha to the border of the Namib Desert. These melons grow slightly larger than softball-sized, and they look simply luscious as the landscape dries up, like green and gold packages of life-saving moisture. They lasted much longer than we would have expected, and in our travels we asked about their natural history: We heard that the melons can be very bitter, but that kudu and gemsbok will bite into them as other resources become scarce. At Namib-Rand, Mr. Klein collected several on our tour of the reserve and said that some plants produce bitter fruit, but others taste quite nice. The ones he selected were on the “nice-tasting” end of the spectrum, a cucumber taste crossed with watermelon consistency, harboring enormous seeds that are probably also edible if prepared correctly. At Treesleeper, with the Bushmen, we ate sweet berries, which tasted like tamarind but were mostly husk, seed, and a little fruity essence.

We missed one natural Namibian delicacy – not a plant, but a fungus. In February and March, as we drove the B-roads between Windhoek and the coast, we regularly saw people standing by the side of the road with white mushrooms as big as their heads. We were still a little dubious about food safety at this point, so never stopped, but in late April we learned from several Namibian friends that the mushrooms taste amazing as steaks sauted in butter. We should have stopped and paid no more than N$30 for one, as long as it was treated properly and not held upside down, which causes dirt to fall into the gills. In such a dry country, mushrooms are pretty rare, but these grow on termite mounds because these mound-building termites farm fungus. The mycelia send up fruiting bodies when there’s rain.

This year’s winter was not as cold as we’d been warned to expect, even at elevation in Windhoek. We never used our heaters in the apartment and never awoke to frost, although we did pass many people bundled in puffy jackets, or selling gloves on the street. Winter usually brings east winds on the coast. These hot winds are caused by freezing temperatures in the mountains, which set up a pressure differential with the coast. As the air moves from high (cold) to low (warm) pressure, it also drops in elevation, and the air heats up from this adiabatic change. When the air reaches the coast, it can be 40C, driving desert sand before it at such velocity that it sand-blasts paint off cars and knocks small children off cliffs (this latter in theory – we never tested it). The hot air is also essential for drying out the guano on the big platform constructed above one of the salt pans. Usually, the guano is “harvested” in June, but this year the process didn’t start until September. Once again, it’s proving to be a weird year - the east winds were late and infrequent.

In Namibia, the country burns in August. In general, we’ve tried to avoid driving at night in a country where the wildlife is larger than our Kombi, and the wildlife habitat comes up to the edge of the (dark, narrow, 2-lane) road. But on a couple of August nights, we were traveling after sunset through scenes out of Dante’s Inferno. Pitch black. Red flames licking through low bush. Lines of fire stretching into the air as they moved up hillsides. Thick smoke. We have heard that some of these fires are set on purpose, because they flush game, eliminate accumulated grass litter, and open up space for new vegetation growth. Indeed, we have seen green blades appear in burned-over areas. Some of the fires are probably natural or unintentional: the landscape is so dry by late winter that it seems poised to combust.
In Namibia, spring arrives in September. Despite the ongoing dry weather, some of the Acacia trees flower, and there’s a heady sweetness in the air. From our 7th floor apartment, Windhoek looks like a patchwork of purple, because all the introduced (from Australia/NZ?) Jacaranda trees are covered in purple blossoms. Historically, spring was the “little rainy season,” but the recent trend has been that Namibia receives less and less of its annual rainfall during this season. We have heard October called “suicide month”, the hottest month of the year, when clouds start gathering after months of blue-sky, dry weather. The farmers think that these clouds might drop some rain and end the seasonal drought, filling their catchments and growing a bit of new vegetation for their stock. But usually all they get is clouds, not rain. This year, however, we’ve witnessed a little rain as October ends, including unprecedented sprinkles at Swakopmund and 40 mm in a night in Windhoek. We wonder what this signals for the ocean, which is roiling around with odd winds and high production, and there may be another sulfide eruption in store…. This time, if the toxic ocean materializes, we hope to be out on the water of Walvis Bay to study it intensively first hand.

Arrival

It is a long way from Seattle to Namibia... and yet short. On the last day of 2007, we left the damp chill rain that never seems to dry, and we arrived a year later, having weathered 3 plane flights by dint of Katie playing with other kids on the first leg, sleeping on the second and third.

On the last leg from Johannesburg to Windhoek, we encountered a dry landscape of gigantic proportions. Initially, we flew over rich neighborhoods of Jburg where nearly every house had a private swimming pool. On the outskirts, the proportions shrunk, and the colors shifted from green to redbrown: neighborhoods of dirt roads, smaller houses, little vegetation to overcome the aerial sense of stark poverty. From above, it is clear that there are still two classes of people living in different ways in different places. The dirt underlying sparse vegetation shows red-brown especially as a mark of humans. The roads are red, running arrow-straight to the horizon, or coming together like a few spokes of a wheel around a red town, where light glints off some roofs. The fields are red, often solitary patches in the natural landscape, and even though we expected them to be green from mid-summer production. Close to Johannesburg, we saw crop circles that were obvious evidence of irrigation, but further away most fields appeared empty. By the time we reached Namibia, crop fields were not apparent at all, instead large fenced pastures. The fence borders are also red, probably from vehicle patrol rather than animals. Much of the flight took us over the Kalahari desert in Botswana, where evidence of humans is particularly sparse. Instead, the landscape is marked by irregular round grey depressions, some reaching the size of villages we saw along the way. At least they looked like depressions from above. Initially I thought meteorites, but the marks are much too common for that to be likely. Alan thinks the marks are water holes, small depressions that collect water. He is usually correct about these sorts of things, but most of the areas currently contain neither water nor vegetation, and they do not have obvious “game” trails around them (although in retrospect, I think we were too high to see paths of that size).

On the drive from the airport into Windhoek, we saw baboons, ostrich, kudu, warthogs, ant mounds, weaverbird nests. Crickets sing at night. Everything about the natural landscape looks different - we are continually wondering what things are and why the land looks as it does. And looking forward to learning more.