The objective of this trip was to meet oyster growers. We had a spectacular drive from Windhoek to Henties Bay on Jan 30, newly ensconced in the Combi (VW van). We passed through a blizzard of butterflies – they seem to be bursting forth in droves just on the edge of where it’s rained. And we passed underneath a maelstrom of hawks, literally hundreds of them circling and zooming across the road, reason unknown. It was particularly surprising to find them all together since we’d commented so often on the striking absence of raptors – we’d seen less than a dozen in our travels of the previous month. We took the sand road “short cut” to bypass Swakopmund and go straight to Henties Bay, past the Spitzkoppe, a dramatic promontory that rises from the flat sandy plain in a series of sheer drops from rounded peaks. All along the road, tables were set out with rocks for sale, crystals of a variety of colors. (We have yet to visit the Crystal Museum in Swakopmund, which boasts the biggest crystal in the world, almost twice the height of a person. And of course we won’t visit the vast stretches of coast that are closed to entrance because of diamonds being collected from the sand.) On this road, we were also treated to our first experience of springbok “pronking”. They bounce, apparently straight-legged, a few meters straight up – a sign of vague unease that the Combi had stopped so the people inside could appreciate the two-dozen animals in the small herd. Springbok are excellent desert-dwellers because they never need to drink, getting sufficient water in the vegetation they eat.
One weekend morning this trip, we traveled north from Henties Bay for less than an hour to Cape Cross, which is famous for tens of thousands of Cape Fur Seals. Certainly, we’d had a fine look at them at Walvis Bay, but the Cape Cross colony was pretty amazing. The rocks were polished from generations of seals sliding across them, and the depressions in between boulders were filled with scat and carcasses, tiny skulls showing white through reddish-brown background. The smell was incredible – I actually took a shower that evening because I was convinced I could still smell seal in my hair! Also on the beach was an enormous dead sea turtle – Alan says its head was the size of a basketball and total length around 15 feet. I thought less but still impressive… and sad that such a giant is no longer roaming the oceans. The seals seemed a little more expendable, with pups rolling on and off the beach in the surfable waves – only the ones at the upper edge of the ribbon of seals along the shoreline seemed to stay put, mostly sleeping and covered in sand. The pups are darker than the adults (also, of course, smaller), so it seemed to us that most of the mothers must be off hunting for fish, or perhaps just sleeping offshore, flippers held out of the water, away from all the fuss. When mothers returned, they would bellow and haul themselves through the pack of seal bodies (adults snapping at them as they jostled and bumped), presumably looking for their own pup among the thousands there on the beach. We saw one mother very deliberately keep all pups away except one, which she let nurse.
The meetings with growers were great. We heard some familiar stories, hemispheric restatements of the problems experienced in Washington: difficult markets, mass mortalities of unknown cause, clients stolen away by other growers who undercut prices, nearby practices that exacerbate a pest problem…. The primary cultivated species is the Pacific oyster, Crassostrea gigas, which has been introduced to the US west coast, Namibia, and more than 60 other countries. As far as we have seen here, it has not established. We are puzzled by this, because the growers are complaining that the oysters are soft with gonad (spawn-y, or even spawned out), reflecting high summer water temperatures. The temperatures may be particularly high this year because, essentially since our arrival in Namibia, this high-upwelling coast has not been upwelling! The winds have blown from the northwest, pushing surface water onshore, keeping the deep cold water down deep, and allowing the warm Angola Current to push southwards to Namibia. Water temperatures have been recorded in Swakopmund and Walvis Bay around 25C (quick translation: 77F), perfectly suitable for oyster larvae to survive and grow. Yet, no spat have appeared – in Walvis Bay, the larvae may simply not be retained in this small indentation in the coast.
The methods for growing oysters differ between Namibia and Washington. The oldest oyster company (young by US standards: second generation) is actually a tiny arm of a much larger company that produces salt (and seabird guano). Seawater is pumped up several meters and then flows by gravity through a series of ponds where water evaporates, impurities (gypsum) are precipitated out, and finally sandy salt is removed in foot-cube chunks for further refining. In its initial path, the seawater is divided into two ponds: a 30-ha pond, mostly <1 m deep, has racks for growing oysters, and a slightly larger pond contains the platform to attract cormorants to breed (and defecate). Mr Klein produces his own cultchless spat by raising larvae in tiny upwellers with ambient seawater, then allowing them to recruit onto smooth plastic sheets and brushing spat off daily – both C. gigas and Ostrea edulis (the only grower on the Namibian coast to produce edulis). Larger oysters are planted into the pond in open-top mesh bags/trays, just below the water surface. Oysters are packed into the trays, but the salt pan soup of phytoplankton must be incredibly rich, fueled both by the ocean inputs and by recycled nutrients from birds. Because of the importance of these shallow-water (albeit salty) habitats for birds, the whole salt company is also a game preserve! Even with our ornithologically naïve eyes, we’ve seen 2 flamingo species, 2 cormorant species, grebes, African ducks, turnstones, at least 4 tern species, and long-legged stilt-like birds with both upturned and downturned bills.
Mr Klein described the following food web in the salt pond “chemostat” where he grows oysters: Flamingos remove most of the organisms in the sediment. Fishing birds such as terns and cormorants feed on the fish (which include “freshwater” tilapia at 40 ppm!). Fish feed on the red alga Gracilaria (deliberately introduced as a prospective aquaculture product, because it can be refined to produce agar), and perhaps also on goggas (Afrikaans, so make sure the “g’s” are raspy in your throat) – Paridotea isopods. Mr Klein observed that, coincident with his introduction of Gracilaria, a pest of his oysters disappeared: polychaete worms that bore through the shell and cause mortality and disfigurement. He wonders if the Gracilaria provided a refuge for the isopods, which then removed the worms. Is this a cool food web, or what?!??? We are likely to work on testing these interactions while we are here. Of course, there are problems, such as: 1) we haven’t been able to find the polychaete worm at all, so it may be locally extinct from the salt pond (perhaps was even introduced with oysters from Chile or the US) – not because of isopods, but because of high salinity. If the worms are no longer present, it will be difficult to test whether isopods control the worms. 2) Worldwide, boring polychaetes in oysters are controlled by dipping oysters in high-salt baths (hmmm, like a salt pond) or moving the oysters onto wooden racks off-bottom (hmmm, did some husbandry practices change at the same time the Gracilaria was introduced?). So the isopods might not be responsible for a rapid decline in worms.
Most of the oyster growers other than Mr Klein are based in Walvis Bay, where oysters are grown exclusively by suspended culture in water that tends to be less than 15 m deep. There are less than 20 companies, some of which are just a few years old. Originally, in Walvis Bay, bags were suspended from wooden platforms, but now the dominant method is “Spanish longlines”. Blue plastic 55-gallon drums are used as floats, and single (cultchless) oysters are placed in stacks of trays suspended from the floats and lines in between them. Two major sources of mortality for the oysters appear to be: low oxygen conditions lasting more than a week during sulfide eruptions – the water can be deoxygenated right up to the surface; and stressful summer conditions, involving unknown combinations of high temperatures and pathogens. Right now, as downwelling conditions persist, and the warm Angola Current pushes south, many mass mortality events have been reported, with up to 60% crop loss. Given the millions of dollars spent worldwide to understand “summer mortality”, and the general conclusion that the only remedy is to raise genetically tough oyster families, we probably won’t get deeply involved in research on this problem – no one approaches it from an ecological perspective. Fortunately, from the growers’ perspective, one company has a beautiful hatchery facility and produces millions of spat from local broodstock.
Showing posts with label Henties Bay. Show all posts
Showing posts with label Henties Bay. Show all posts
Saturday, February 16, 2008
Sunday, January 20, 2008
Week 2 trip to the coast
Jan 8-13 2008 (Tuesday-Sunday):
We traveled by car from Windhoek to Henties Bay on the west coast, which took about 5 hours with just two brief stops (for gas and for Katie to pee in the desert) along the way. Alan drove slower than all but two large trucks (one carrying cows), but was still averaging over 100 kph on “tar roads” (paved) and slightly slower on the “salt road” along the coast.
The drive shows a gradient from semi-arid savannah to almost pure sand. We began in a now-familiar landscape dominated by acacia trees. The grasses in the ground cover seem entirely dry, but nevertheless were being collected in huge bags by groups of people along the road. We suspected they were using the grass as animal forage. We saw some goats, and a tannery/stock pens. Farther from Windhoek, we began to see “wild” animals as well, a few springbok, several troops of baboons, termite mounds, and warthogs. The distribution of termite mounds and warthogs seemed almost perfectly correlated, with a center around the “garden city” of Okahandjo, which must have a reliable water source to be able to grow olives and tomatoes. As we drove farther west, the grass in the understory turned to short brown tufts, and the acacia trees became smaller and sparser. Along the whole drive, we saw distant mountains, each set seemingly different in geology, based on color (from grey to red) and shape (from mounded to spikey). There were only two more sizable settlements along the way to the coast, at Karibib and Usakos, nestled in a large depression that must bring some water. After Usakos, the fences that had lined the highway throughout the rest of the trip dropped out, and we saw no more animals. Although the “rest” signs still showed a picnic table under a tree, instead these rest areas had a permanent awning – no trees available anywhere. As we approached Swakopmund, I finally understood how huge the landscape of Namibia appears, with an arcing blue sky and vast panorama of arid ground to the distant mountains: the ocean looked small in comparison! Probably the close curtain of fog over the ocean contributes. We turned north from Swakopmund, leaving behind us the enormous red dunes just to the south. On the beach side, we saw many restrooms, but the coast was quite deserted except for a few fishers with poles so long that they attach them for transport to the front bumper, sticking up in the air. On the far side of the road, which was still hard and flat despite no asphalt, we saw only one type of low-lying bush that accumulates sand into mounds. When we saw them up close later in the evening, the accumulated sand is riddled with animal burrows. The plants could be huge Salicornia, by the round succulent shape of stems and leaves. We also passed an area of salt-lichen, closed to off-road traffic. It appeared red-brown and quite large, maybe 10-20 cm aggregations, at least as we passed at speed and distance in the car.
When we arrived at the Sam Nujoma Marine Resources Research Center, we were welcomed into the Director’s suite, as the director had quit and left the day before. The center is 4 years old, and directors apparently have a difficult time dealing with its infrastructure challenges, low usage, and remote location. It’s actually quite a remarkable place: the architect designed the buildings at odd angles so they appear already to be crumbling off the sand cliff into the sea (perhaps that was not his intention), and an underground river has its mouth here, so freshwater is easily accessible from wells (there are small green lawns and numerous horticultural projects). In fact, the freshwater flow is so large that it leaves a small 2-m lens of saltwater on the surface, where all the marine organisms live. And the remainder of the water column along this stretch of coast is fresh and often anoxic. SaNuMaRC has delighted, surprised, and puzzled us. It was established with an elaborate plan of “closing the loop” to achieve sustainability, but the solar hot water heater is broken and water runs continuously, the biogas digester apparently doesn’t work because the septic truck came twice for pump-out, the horticultural plants include two notorious invaders of arid land (Opuntia and tamarisk), and the chicken, geese and ducks brought in for pest control have been caged (against hyenas and because they ate plants instead). We were also puzzled by the placement of the center: no thoughtful ecologist would have selected the place because of the low diversity on the exposed beach. No thoughtful lab scientist would have selected the place because there is no running seawater – despite 4 years of trying, it has been a recent breakthrough to establish a permanent pipe to fill carbuoys with “good” seawater at the bottom of the dune, then truck it to the top. Communication with the outside world is through UNAM’s network, which makes email decidedly slow (many minutes simply to load a web page) especially during weekdays when others are also on the network. Alan removed a bulb from a dissecting ‘scope with no plug to replace the burned-out bulb in the second ‘scope, allowing us to examine algae. The library mostly contains material about UNAM, with just a handful of reference books – although, given how little we know about natural history, the perfect number to get us started. We wondered what political decision was made to place the center in this remote location and invest so much in buildings rather than equipment to expedite science: then we found out that Sam Nujoma has a house just down the street in Henties Bay! Scientists and staff at the center bought fish for Nujoma and entourage; and Saturday near sundown the same vehicle returned with two loads of boxes that were put into the common room – possibly the empty, unplugged walk-in freezer (Alan had checked it out from curiosity earlier in the day). Mystery!
We have been impressed by many of the horticultural projects, especially growing different varieties of squashes and melons to look for resistance to salt spray (imagine! Watermelons growing out of sand!), and successful production of oyster mushrooms (these grow out of the end of plastic bags in a special room). Even with limited seawater, there are also projects to raise marine fish in tanks.
SaNuMaRC, like much of Henties Bay, perches above a restless ocean on a red-sand dune: the beach sand is gray, and the old river sand purple in places. This beach has some similarities to the one we left on the outer coast of Washington: extensive sand (for hundreds of miles, rather than tens) that people drive on (with Land Rovers and quad bikes rather than pick-ups). Signs all indicate that it is illegal to drive on beaches, but the enforcement is apparently lax. People drive 4x4 vehicles to set up elaborate day-camps for fishing and kite-flying; and they drive quad bikes up and down the steep sand cliffs that plunge 20-30 m to the beach. We observed that almost everyone driving on the beach was white, and we’ve heard people come from all over Africa because these beaches are some of the last remaining where it is possible to drive. Some of the roadside trash suggests that fireworks were set off over New Years as well.
We’re beginning to learn about the Namibian coast by walking the beaches at low tide. The beaches themselves are quite barren, reflecting the dynamic movement of sand – 1 m per week northward movement, and perpetual rearrangement of berms and slopes. One day, water was trapped in a high intertidal pool and Katie went swimming in comfortably warm water up to her thighs. The next day the pool simply drained away. We found just two species in the sand: sand-colored isopods up to nearly 1 cm in length, which nibbled on toes but burrowed rapidly in the sand, presumably food for the few shorebirds we’ve seen. And Donax surf clams – Pismo clams in California – that work their way up and down the beach in the swash. Alan traded a local fisherman some beach-cast tackle for information that the clams are quite rare near the marine station, but become more abundant a few km N and S where the sand quality changes. We found a few shells, some recently opened for bait, and two moribund individuals that allowed us to see internal anatomy: a large digger foot and two siphons, too small to make anything but bait or chowder.
The wrack on the beach is slightly richer, dominated by Laminaria kelp and a small 1-2 cm native mussel. Elsewhere, this Laminaria is collected for cultured abalone food, but it is probably too rare to grow much of a business: there’s just not sufficient hard substrate along the coast to support vast kelp forests. We also heard that the small native mussel is such an effective fouling organism that is preventing the expansion of Mytilus galloprovincialis from S. Africa north along this stretch of coastline. In the wrack we found two morphological types of larger mussels: one is quite elongate and brown, with an outer edge that is almost square in shape; the other is jet-black with a white-to-blue abraded umbo and sharp angle on the shell edge near the hinge – perhaps gallo. At the low, large patches of mussel shell rolled around in the surf, almost flowing like water up and down the beach. The wrack also included smaller numbers of: limpets, a translucent brown circular shell, snails, Venerupis clam shells, sea cucumbers, bryozoans – primarily one that forms long, narrow, flat colonial blades, crab carapaces, and parts of spiny lobsters. We have begun to look at some of the algae and have found, in addition to Laminaria pallida, ulvoids and Cladophora for greens, and numerous reds. Some look familiar, such as Plocamium and Ceramium, but some were really impossible to tell. We had two books at our disposal: some color plates and descriptions in the Seaweeds of southwest Africa, and line drawings in Branch and Branch’s guide to seashores. But the reds included some fascinating types, for instance one that appeared to have no holdfast but instead twined around Cladophora filaments, and another with dramatic flower-like reproductive structures emerging in patches from a flat blade. We did find one deadly species - Physalia (Portugese man-o-war), which blew in droves onto the beach as the wind shifted from NW to SW one afternoon. Alan collected a whole bucketful, along with the similarly-blue Velella velella (By-the-wind sailor), which is common on the beaches of Washington.
We’re also learning about the Namibian coast by talking with scientists: Larry Oellermann, who is on a multi-year contract at SaNuMaRC to improve mariculture, and several people at NatMIRC (National Marine something research center) in Swakopmund, the major research site for the Ministry of fisheries and marine resources. The Benguela system is one of permanent upwelling, not intermittent. Generally there are strong winds from the southwest (although mostly northwest during this stay), with occasional shifts to the east that bring terrible (to people) but dune-nourishing sand. Plus flies. The water was soupy green, even in the tidepool caught by sand, and the high-tide waves were frothy with diatoms. This sounds tremendous for marine production: Even here, however, wild finfisheries are collapsing (we heard that sardines are essentially gone, although the fish identification book in the library indicates they are now carefully managed and sustainably harvested! Offshore, orange roughy and Patagonian toothfish, both long-lived, slow-to-mature deepwater species, began to be exploited around 1995, and in just a few years catch per unit effort plummeted.) And last year 60% of the oyster crop was lost to sulfur “blooms”. The fishery and mariculture troubles probably have different causes, and interestingly sulfur appears entirely natural. High production in the coastal ocean contributes to a rain of organic material reaching the bottom, where it accumulates and is decomposed by such things as the largest bacterium ever discovered (1 mm cells!). Decomposition creates pockets of hydrogen sulfide that, for reasons yet unknown (at least 15 hypotheses have been suggested), occasionally bubble out over the course of a week or so: the hydrogen sulfide reacts with oxygen in the water column to create water and elemental sulfur. This elemental sulfur is visible in satellite imagery as an enormous patch of light-blue off of the coast. And locally it appears as anoxic water all the way to the surface: immediately bad for many fish and crabs, and intolerable by Pacific and European oysters after about a week (whether from the sulfide or anoxia is not clear). Some of the native species (a goby, mussels, clams) apparently last longer.
We traveled by car from Windhoek to Henties Bay on the west coast, which took about 5 hours with just two brief stops (for gas and for Katie to pee in the desert) along the way. Alan drove slower than all but two large trucks (one carrying cows), but was still averaging over 100 kph on “tar roads” (paved) and slightly slower on the “salt road” along the coast.
The drive shows a gradient from semi-arid savannah to almost pure sand. We began in a now-familiar landscape dominated by acacia trees. The grasses in the ground cover seem entirely dry, but nevertheless were being collected in huge bags by groups of people along the road. We suspected they were using the grass as animal forage. We saw some goats, and a tannery/stock pens. Farther from Windhoek, we began to see “wild” animals as well, a few springbok, several troops of baboons, termite mounds, and warthogs. The distribution of termite mounds and warthogs seemed almost perfectly correlated, with a center around the “garden city” of Okahandjo, which must have a reliable water source to be able to grow olives and tomatoes. As we drove farther west, the grass in the understory turned to short brown tufts, and the acacia trees became smaller and sparser. Along the whole drive, we saw distant mountains, each set seemingly different in geology, based on color (from grey to red) and shape (from mounded to spikey). There were only two more sizable settlements along the way to the coast, at Karibib and Usakos, nestled in a large depression that must bring some water. After Usakos, the fences that had lined the highway throughout the rest of the trip dropped out, and we saw no more animals. Although the “rest” signs still showed a picnic table under a tree, instead these rest areas had a permanent awning – no trees available anywhere. As we approached Swakopmund, I finally understood how huge the landscape of Namibia appears, with an arcing blue sky and vast panorama of arid ground to the distant mountains: the ocean looked small in comparison! Probably the close curtain of fog over the ocean contributes. We turned north from Swakopmund, leaving behind us the enormous red dunes just to the south. On the beach side, we saw many restrooms, but the coast was quite deserted except for a few fishers with poles so long that they attach them for transport to the front bumper, sticking up in the air. On the far side of the road, which was still hard and flat despite no asphalt, we saw only one type of low-lying bush that accumulates sand into mounds. When we saw them up close later in the evening, the accumulated sand is riddled with animal burrows. The plants could be huge Salicornia, by the round succulent shape of stems and leaves. We also passed an area of salt-lichen, closed to off-road traffic. It appeared red-brown and quite large, maybe 10-20 cm aggregations, at least as we passed at speed and distance in the car.
When we arrived at the Sam Nujoma Marine Resources Research Center, we were welcomed into the Director’s suite, as the director had quit and left the day before. The center is 4 years old, and directors apparently have a difficult time dealing with its infrastructure challenges, low usage, and remote location. It’s actually quite a remarkable place: the architect designed the buildings at odd angles so they appear already to be crumbling off the sand cliff into the sea (perhaps that was not his intention), and an underground river has its mouth here, so freshwater is easily accessible from wells (there are small green lawns and numerous horticultural projects). In fact, the freshwater flow is so large that it leaves a small 2-m lens of saltwater on the surface, where all the marine organisms live. And the remainder of the water column along this stretch of coast is fresh and often anoxic. SaNuMaRC has delighted, surprised, and puzzled us. It was established with an elaborate plan of “closing the loop” to achieve sustainability, but the solar hot water heater is broken and water runs continuously, the biogas digester apparently doesn’t work because the septic truck came twice for pump-out, the horticultural plants include two notorious invaders of arid land (Opuntia and tamarisk), and the chicken, geese and ducks brought in for pest control have been caged (against hyenas and because they ate plants instead). We were also puzzled by the placement of the center: no thoughtful ecologist would have selected the place because of the low diversity on the exposed beach. No thoughtful lab scientist would have selected the place because there is no running seawater – despite 4 years of trying, it has been a recent breakthrough to establish a permanent pipe to fill carbuoys with “good” seawater at the bottom of the dune, then truck it to the top. Communication with the outside world is through UNAM’s network, which makes email decidedly slow (many minutes simply to load a web page) especially during weekdays when others are also on the network. Alan removed a bulb from a dissecting ‘scope with no plug to replace the burned-out bulb in the second ‘scope, allowing us to examine algae. The library mostly contains material about UNAM, with just a handful of reference books – although, given how little we know about natural history, the perfect number to get us started. We wondered what political decision was made to place the center in this remote location and invest so much in buildings rather than equipment to expedite science: then we found out that Sam Nujoma has a house just down the street in Henties Bay! Scientists and staff at the center bought fish for Nujoma and entourage; and Saturday near sundown the same vehicle returned with two loads of boxes that were put into the common room – possibly the empty, unplugged walk-in freezer (Alan had checked it out from curiosity earlier in the day). Mystery!
We have been impressed by many of the horticultural projects, especially growing different varieties of squashes and melons to look for resistance to salt spray (imagine! Watermelons growing out of sand!), and successful production of oyster mushrooms (these grow out of the end of plastic bags in a special room). Even with limited seawater, there are also projects to raise marine fish in tanks.
SaNuMaRC, like much of Henties Bay, perches above a restless ocean on a red-sand dune: the beach sand is gray, and the old river sand purple in places. This beach has some similarities to the one we left on the outer coast of Washington: extensive sand (for hundreds of miles, rather than tens) that people drive on (with Land Rovers and quad bikes rather than pick-ups). Signs all indicate that it is illegal to drive on beaches, but the enforcement is apparently lax. People drive 4x4 vehicles to set up elaborate day-camps for fishing and kite-flying; and they drive quad bikes up and down the steep sand cliffs that plunge 20-30 m to the beach. We observed that almost everyone driving on the beach was white, and we’ve heard people come from all over Africa because these beaches are some of the last remaining where it is possible to drive. Some of the roadside trash suggests that fireworks were set off over New Years as well.
We’re beginning to learn about the Namibian coast by walking the beaches at low tide. The beaches themselves are quite barren, reflecting the dynamic movement of sand – 1 m per week northward movement, and perpetual rearrangement of berms and slopes. One day, water was trapped in a high intertidal pool and Katie went swimming in comfortably warm water up to her thighs. The next day the pool simply drained away. We found just two species in the sand: sand-colored isopods up to nearly 1 cm in length, which nibbled on toes but burrowed rapidly in the sand, presumably food for the few shorebirds we’ve seen. And Donax surf clams – Pismo clams in California – that work their way up and down the beach in the swash. Alan traded a local fisherman some beach-cast tackle for information that the clams are quite rare near the marine station, but become more abundant a few km N and S where the sand quality changes. We found a few shells, some recently opened for bait, and two moribund individuals that allowed us to see internal anatomy: a large digger foot and two siphons, too small to make anything but bait or chowder.
The wrack on the beach is slightly richer, dominated by Laminaria kelp and a small 1-2 cm native mussel. Elsewhere, this Laminaria is collected for cultured abalone food, but it is probably too rare to grow much of a business: there’s just not sufficient hard substrate along the coast to support vast kelp forests. We also heard that the small native mussel is such an effective fouling organism that is preventing the expansion of Mytilus galloprovincialis from S. Africa north along this stretch of coastline. In the wrack we found two morphological types of larger mussels: one is quite elongate and brown, with an outer edge that is almost square in shape; the other is jet-black with a white-to-blue abraded umbo and sharp angle on the shell edge near the hinge – perhaps gallo. At the low, large patches of mussel shell rolled around in the surf, almost flowing like water up and down the beach. The wrack also included smaller numbers of: limpets, a translucent brown circular shell, snails, Venerupis clam shells, sea cucumbers, bryozoans – primarily one that forms long, narrow, flat colonial blades, crab carapaces, and parts of spiny lobsters. We have begun to look at some of the algae and have found, in addition to Laminaria pallida, ulvoids and Cladophora for greens, and numerous reds. Some look familiar, such as Plocamium and Ceramium, but some were really impossible to tell. We had two books at our disposal: some color plates and descriptions in the Seaweeds of southwest Africa, and line drawings in Branch and Branch’s guide to seashores. But the reds included some fascinating types, for instance one that appeared to have no holdfast but instead twined around Cladophora filaments, and another with dramatic flower-like reproductive structures emerging in patches from a flat blade. We did find one deadly species - Physalia (Portugese man-o-war), which blew in droves onto the beach as the wind shifted from NW to SW one afternoon. Alan collected a whole bucketful, along with the similarly-blue Velella velella (By-the-wind sailor), which is common on the beaches of Washington.
We’re also learning about the Namibian coast by talking with scientists: Larry Oellermann, who is on a multi-year contract at SaNuMaRC to improve mariculture, and several people at NatMIRC (National Marine something research center) in Swakopmund, the major research site for the Ministry of fisheries and marine resources. The Benguela system is one of permanent upwelling, not intermittent. Generally there are strong winds from the southwest (although mostly northwest during this stay), with occasional shifts to the east that bring terrible (to people) but dune-nourishing sand. Plus flies. The water was soupy green, even in the tidepool caught by sand, and the high-tide waves were frothy with diatoms. This sounds tremendous for marine production: Even here, however, wild finfisheries are collapsing (we heard that sardines are essentially gone, although the fish identification book in the library indicates they are now carefully managed and sustainably harvested! Offshore, orange roughy and Patagonian toothfish, both long-lived, slow-to-mature deepwater species, began to be exploited around 1995, and in just a few years catch per unit effort plummeted.) And last year 60% of the oyster crop was lost to sulfur “blooms”. The fishery and mariculture troubles probably have different causes, and interestingly sulfur appears entirely natural. High production in the coastal ocean contributes to a rain of organic material reaching the bottom, where it accumulates and is decomposed by such things as the largest bacterium ever discovered (1 mm cells!). Decomposition creates pockets of hydrogen sulfide that, for reasons yet unknown (at least 15 hypotheses have been suggested), occasionally bubble out over the course of a week or so: the hydrogen sulfide reacts with oxygen in the water column to create water and elemental sulfur. This elemental sulfur is visible in satellite imagery as an enormous patch of light-blue off of the coast. And locally it appears as anoxic water all the way to the surface: immediately bad for many fish and crabs, and intolerable by Pacific and European oysters after about a week (whether from the sulfide or anoxia is not clear). Some of the native species (a goby, mussels, clams) apparently last longer.
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