Resurfacing of coconuts

Coconut I of my experimental floatations in seawater was marketed, wrapped in plastic, as a “Milky Coconut, Dominican Republic 5711/03 class 1, display until February 8 2005”. The initial mass, inclusive of subsequently removed plastic and coir fibres was 605 g and sank in seawater in February 1 2005 at 15.30 hrs G.M.T. During the first two and a quarter hours air bubbles effused from around two of the three eyes (basal pores) when the coconut was manually inverted from the usual apex-up orientation when sinking. This air presumably came from the nut wall, via canals seen radiating from the inside of the basal pores on split specimens, since the nut exterior changed from light to dark brown in this short time. A wet mass, exclusive of removed coir fibres and plastic was recorded as 607 g after exactly 2.3 of a day in the seawater tank, rising to 611 g on days 2.6 and 11.8. After this the coconut was removed to the bottom of an open bucket used to house the rejected old tank seawater and had a mass of 607 g on day 100, 601 g on day 127 and 598 g on day 200. This water sometimes had a raised density due to evaporation before being exchanged with new water from the sea and this was 1.032 g/ml on day 575 when coconut finally had lost enough internal mass of endosperm and or milky liquid to resurface. It was then returned to the diurnally aerated tank seawater of 1.029 g/ml density where it promptly sank at a mass around 586 g. The displacement volume found by dividing this mass by the density of the two seawaters was therefore 567 to 568 ml, and the initial density when marketed 1.06 g/ml. The cited water densities are from a hydrometer only giving an exact reading at 20°C and actually recorded at 6 hrs G.M.T. on August 31 2006 at 16°C. The air temperature above the bucket had risen to above 77°F (25°C) in the later July 2006 heatwave without causing the coconut to resurface. This suggests that expansion of primary and secondary decay gases by increased ambient temperature is not the direct cause of resurfacing during a relatively cool weather. Probably the high temperatures increased the rate at which the milky liquid and endosperm inside the nut was converted into gas, but due to the still intact nature of the three basal pores and nut wall the gases merely diffused out if their partial pressures were greatly in excess of the ambient and similarly stagnate seawater. In previous experiments, reported from the fresher tank seawater in my articles in The Drifting Seed (2005, 2006) the initially more buoyant coconuts A to F all became gradually less dense during the first 200days of flotation and only then started to gain mass due to a net replacement of their internal primary and secondary gases by seawater. Coconut I is merely following the same trend but on a longer time-scale and with little or no primary air present inside the endosperm cavity when marketed. Some of these coconuts contained little or no milky liquid when marketed and evidence of loss of endosperm flesh under the basal pores before the latter became thin or open enough to admit seawater at an increasing rate in the aerated tank environment. Probably there is a similar decay of endosperm flesh into bacteria plus gas going on to reduce the mass of coconut I, and not merely fermentation of milky liquid which may have actually slowed the decay process in the denser endosperm down? It is predicted that coconut I, now kept in the aerated tank environment will soon resurface due to further internal mass loss.



My tanks. 

Chalkwell Stranded feathers (cont.)

September 3 and 4 2006. Chalkwell beach was revisited around noon on both these days, with predicted tides at 1.6 m above mean sea level forming a strandline of eelgrass (Zostera), brown algae and gull feather on the first morning and cut into a small cliff on the second morning. There was a southwest gale on September 2 and 3 but it was calm at the times of the high tides. The occurrence of eelgrass was a new feature, not very evident earlier in the year and doubtless resulting from the wind acting on the lower intertidal zone, about 2 km south-west of Chalkwell, where this marine grass grows in summer.

On September 3 a couple of hundred metres of the strandline showed three large bird corpses, as well as the separated barred and gull feathers seen previously. A large gull with intact head had stranded against the west side of a breakwater and two headless birds were on the open strandline further to the east. The large gull probably corresponded to the feathers of the Lesser Black-Backed Gull now added to the loose assemblage and one of the corpses was a white smaller gull represented by loose Black-Headed Gull feathers seen previously. Both these corpses had gone the next day but the third one remained having merely been displaced down the cliff of grass and sand cut by the later tide and wind. During this displacement one of the wings had opened but considerable force was required to pull out one of the primary feather of around 320 mm when standing on the corpse. This feather was dark grey with a white rhachis. This feather was not greatly different to those found loose and attributed to the wings of Lesser Black-Backed Gulls, and the smaller transverse banded brest and tail feathers match the loose banded feathers found on August 22 and later. The secondary wing feathers were paler brown, with a white tip to the more blunt tip to the vane. Due to the ongoing bird influenza cares I did not make a more careful study of the corpse and these smaller feathers but judging from the size of the largest wing feathers it is more likely to be a Peregrine Falcon than a Cuckoo, and was clearly different from the colour pattern of a Curlew. However, a Curlew option for the loose banded feathers seen on the beach was reinforced by a collection of probable primary wing feather among the gull and banded feathers on September 4. This feather showed 14 brown triangular bars on the vane and an overall length of 231 mm. Probably it is a mistake to regard the new corpse with small banded feathers on the body as the only or even the main species yielding the small Curlew-like feathers on the strandline.



Black-Headed Gull

Stranding of feathers at Chalkwell

August 22 2006. A further survey of the two latest strandlines between Chalkwell station and Shelter (0.6 km) showed a return to winter debris in the form of the brown alga Ascophyllum among the summer green algae. A few large common crabs were present, a large one with legs stranded dorsal-up and more numerous separated dorsal carapaces stranded ventral-up; concave-up in terms of hydrodynamics. There were also some stranded reeds, twigs and human-worked wood debris, which had not come directly from the marshes as the latest tides were all relatively low (predicted as slightly higher, 2.5 m above mean sea-level in latest tide studies around 1 p.m.). A characteristic feature of August strandlines was evident in the form of abundant adult feathers of Black-Headed Gulls, which were also seen alive and well on the beach, and locally molt at this time. My experience is that when floated in closed plastic bottles of seawater they remain largely intact and still do not sink (since August 9 1999, molted on grass inland at Leigh-on-Sea) but in more agitated and open tanks they soon break-up releasing separated calamus, rhachis and vane fragments which can sink despite initially being hollow and full of air. On December 4 2005 I refloated both dried and recently stranded primary wing feathers of the Great Black-Backed Gull Larus marinus L, mainly cut into the calamus (quill) and the remaining rhachis plus vane, in the diurnally agitated seawater tanks. The six calamus sample had cut dimensions of 145 mm boy 6 mm diameter, and their separated vanes had lengths ranging from 213 to 247 mm. Recently a few of the calamus samples have sunk apparently unchanged, while the others have lost all or most of their vanes and distal rhachis before sinking. By August 30, day 269 of floatation in the more open conditions there were just two calamus samples still floating horizontally, with one uncut feather which is not reduced to a total length of 350 mm lacking any trace of a vane and the tip of the rhachis. By contrast the black cormorant tail feather, stranded and refloated in the same experimental conditions on January 3 2006, sank in a macroscopically intact condition on August 4 (day 212). The black melanin probably resists decay and brittleness of the white keratin, but there is probably a better adaptation of the deep-diving feathers of cormorants against waterlogging. In addition they have a greater initial density, making them sink quicker when refloated than the relatively hollow structure of gull and other more typical bird feathers. This denser structure and the melanin doubtless contributes to their lower rate of decay, which in gull feathers is due to brittle fracturing of the keratin, rather than obvious bacterial growth. However it is also possible that cormorant feathers also contain more wax or oils than gull feathers. One can of course see the cormorants standing with their wings open to dry them while the gulls and other marine birds do not bother and are much better fliers despite this careless indifference to feather drying. Terrestrial birds even go to the trouble of getting their feathers wet in freshwater, rather than worry about his effect on wing density after a bath.

The more unusual and attractive feathers seen stranded on August 22 have continued to float in the same tank until August 30 without showing signs of damage. A sample of 8, with lengths of 116 to 131 mm and vane widths of 18 to 38 mm (when dry), showed the common characteristics of 8 to 12 transverse brown bands or triangular bars on the generally white background of the vane. The calamus and rhachis were mainly white, but with a grey more translucent proximal end to the calamus, and a shore central band of brown within the white proximal end of the rhachis. It was not clear to me what these feathers were, but since they were spread out on two adjacent strandlines over a 0.6 km distance they did not result from a single drowned woodpecker or similar non-marine species. The tail and secondary wing feathers of a local wading bird the Curlew Numenius arquata (L.) seem to be the most likely candidate judging from Tracks and Signs of the Birds of Britain and Europe by Brown et al. (2003, Christoper Helm, Publisher London 333 pp.). The main problem with that identification is that the similar-looking, larger primary wing feathers, were not seen among the gull feathers of that size; perhaps because they are not molted at the same time as the secondary and tail feathers.

Incidentally the two large pinecones floated and described on April 7 2006, also sank on the tank containing the gull calamus samples on August 2-4 after slight cooling of the warm seawater.