Island Of Helgoland Research Articles

Life-history strategies of calanoid congeners under two different climate regimes: a comparison

Abstract To evaluate the relationship between different environmental temperature regimes and life-history traits of key planktonic taxa, the life cycles of congener pairs of Temora and Centropages species at two sites, a cold-temperate shelf sea (Helgoland Island, North Sea) and a warm-temperate oceanic site (Bay of Villefranche, Mediterranean) were compared in a multi-annual time-series. In an attempt to assemble a variety of parameters – some detailed, others sporadically measured – a synthesis of the life cycle is presented for each population. Although closely related, congeners showed distinct temperature preferences and specific adaptations of their life cycles to temperature regime. On the other hand, co-existing species such as T. longicornis and C. hamatus in the North Sea showed some analogous life-history traits. C. typicus occupied an intermediate position and was able to tolerate both temperature regimes by shifting its reproductive period between seasons. We point out interannual and inter-site variability in the populations investigated and identify the unsolved questions in regard to the seasonal dynamics of these species that require verification.

Stable oxygen isotopes as recorders of salinity and river discharge in the German Bight, North Sea

A high-resolution sediment core (sedimentation rate ~2 mm/year) from the German Bight was analysed for its foraminiferal stable oxygen isotope (δ18O) composition. These data were correlated with instrumental summer sea-surface temperature and salinity data from the nearby island of Helgoland, reaching back 100 years. Comparing the isotope data with the instrumental records reveals a distinct δ18O–salinity relationship (δ18O=0.34×S−9.36; r=0.86) for the German Bight, where salinity is mainly driven by freshwater input from the Elbe River. Thus, these findings provide the possibility for future regional paleosalinity and paleodischarge reconstructions for times far beyond the instrumental timescale.

MSP007 Phenotypic and molecular characterization of Brucella strains isolated from marine mammals of the german North Sea

The prey spectrum of grey seals has to date been described as largely consisting of different fish, cephalopod and shrimp species. On the German island of Helgoland Düne, where harbour seals (Phoca vitulina) and grey seals (Halichoerus grypus) co-occur, a young male grey seal was observed in 2013 and again in 2014 preying upon young harbour seals. A harbour seal carcass with severe traumatic lesions was retrieved and post-mortem examinations were performed. In the following weeks several carcasses showing similar lesions were found. Sightings of grey seals assumed to be preying on harbour porpoises have increased around the North Sea.Increased competition as well as individualised behaviour could explain the increased number of observations, but former cases of abnormal lesions of marine mammals attributed to for example predation by sharks or mechanical processes should be revisited with regard to the emerging knowledge.

Depositional history of the Helgoland mud area, German Bight, North Sea

The Helgoland mud area in the German Bight is one of the very few sediment depocenters in the North Sea. Despite the shallowness of the setting ( 13 to ~1.6 mm/year. Among a number of major environmental changes in this region during the Middle Ages, the disintegration of the island of Helgoland appears to be the most likely factor which caused the very high sedimentation rates prior to 1250 a.d. According to historical maps, Helgoland used to be substantially bigger at around 800 a.d. than today. After the shift in sedimentation, a continuous and highly resolved paleoenvironmental record reflects natural events, such as regional storm-flood activity, as well as human impacts at work at local to global scales, on sedimentation in the Helgoland mud area.

Exploitation of resources modulates stopover behaviour of passerine migrants

The seasonal variation in the supply of ripe Elderberries (Sambucus nigra) on the offshore island of Helgoland (North Sea) was examined from the point of view of the effect of food supply and exploitation on the stopover behaviour of migrating passerines. Elderberries were completely exploited by birds by mid October, three weeks earlier than the last berries disappeared from exclosures. In five out of seven frugivorous passerine species the percentage of trapped birds settling (i. e. recaptured on days subsequent to initial capture) was significantly higher during the period of high availability of ripe Elderberries (early September to early October) than it was earlier (berries still unripe) and later (berries exhausted). No such pattern was observed in fuel deposition rates because rates of body mass change in recaptures differed between periods in only one out of five species. Therefore, in conjunction with the shortage of alternative food, berry supply had an impact on the stopover decision, but did not affect the refuelling itself. The energy demand of migrants as calculated from the number of birds present could not be covered by Elderberries from mid October onwards. Hence, exploitation by earlier migrants reduced the carrying capacity of the stopover site for later migrants, especially when high bird densities were involved. Continent-wide patterns of fuel deposition may have evolved in order to avoid such shortages of food for refuelling just before the crossing of ecological barriers. Passerine migrants would benefit from dispersed resources which allow the avoidance of crowding and exhaustion of supply.

Jannaschia helgolandensis gen. nov., sp. nov., a novel abundant member of the marine Roseobacter clade from the North Sea.

Heterotrophic bacteria were isolated from a water sample taken from the North Sea, 2 km off the coast of the island of Helgoland, by direct plating of the serially diluted sample on complex marine media. Sixteen of 80 strains from the highest sample dilution belonged to the 'Roseobacter-Sulfitobacter-Silicibacter' group within the 2-subclass of the Proteobacteria on the basis of partial 16S rDNA sequence analysis. Phylogenetic analysis of nearly complete 16S rDNA sequences showed that the closest relative of two strains, Hel 10(T) and Hel 26, was Ketogulonicigenium vulgare (94.4% similarity). These strains were Gram-negative, non-motile rods, obligate aerobes, required sodium ions and 1-7% sea salts for growth and did not produce bacteriochlorophyll. Their optimal growth temperature was 25-30 degrees C. The strains had Q-10 as the dominant respiratory quinone. Chemotaxonomic analysis showed a combination of ester-linked 3-OH 10 : 0, 12 : 1 and amide-linked 3-oxo 14 : 0 (or 3-OH 14 : 1) and 3-OH 14 : 0 fatty acids, which appears to be a unique feature of strains Hel 10(T) and Hel 26 within this subsection of the 2-subclass of the Proteobacteria. Based on 16S rDNA sequence analysis and chemotaxonomic data, the strains are assigned to a new genus and species, Jannaschia helgolandensis gen. nov., sp. nov., with the type strain Hel 10(T) (= DSM 14858(T) = NCIMB 13941(T)).

Predation hazard during migratory stopover: are light or heavy birds under risk?

On the offshore island Helgoland, passerine birds killed by predators (feral cats Felis catus and raptors, mainly sparrowhawks Accipiter nisus) during stopover were measured and weighed when found freshly killed and still intact. Supplemented by data of migrating birds ringed on Helgoland and predated on the island later on, age and body mass of victims were compared to live birds trapped on Helgoland during ringing operations. In the eleven species considered, most predator kills fell within the lightest 20% of birds measured during ringing, regardless of which type of predator was involved. It seems that the risk of being heavy due to fuel loads with respect to reduced escape performance is overestimated. The higher exposure of light birds due to more intense foraging and displacement to suboptimal habitats is probably of higher biological significance by offering conspicuous prey for predators. The lower risk of heavy birds when prey of different body condition is available for predators has implications for modelling optimal migration behaviour, and predation risk is perhaps not an important factor for migrants when deciding on site use.

North Atlantic Oscillation and timing of spring migration in birds.

Migrant birds have been trapped on the island of Helgoland (southeastern North Sea) since 1909, with methods and sampling effort remaining unchanged throughout the last four decades. In 12 short/medium-distance migrants and 12 long-distance migrants (23 passerines plus the European woodcock) sample sizes were sufficient to calculate mean spring passage (msp) times and to relate these to climate change. All but one species, passing Helgoland en route to their breeding areas (mainly in Scandinavia), show a trend towards earlier msp-time, which is significant in 7 short/medium-distance migrants and 10 long-distance migrants. The msp-times advanced by 0.05-0.28 days per year, short/medium-distance migrants not differing from long-distance migrants. In 23 out of the 24 species, earlier msp-times coincide with local warmer msp-temperatures (significantly in 11 and 7 species of the two groups, respectively). Even more striking is the relation to a large-scale phenomenon, the North Atlantic Oscillation (NAO), during the last four decades. Again, in 23 out of the 24 species, an earlier msp-time coincides with higher NAO indices (significantly in 9 and 12 species, respectively). The NAO index can also explain differences and similarities in spring migration strategies, as well as migration routes within Europe.

Time allocation in migrating Northern Wheatears (Oenanthe oenanthe) during stopover: Is refuelling limited by food availability or metabolically?

According to full-day observations (scan sampling), Northern Wheatears (Oenanthe oenanthe) stopping over on the island of Helgoland (SE North Sea) during spring and autumn migration spent 51–67 % of the daylight period foraging. Large parts of the day were used for resting or being vigilant, whereas flying, preening and aggressive behaviour were of minor importance. The density of Wheatears did not influence the time devoted to foraging and aggressive behaviour, and the time spent resting/vigilant was not correlated to predation risk (measured as the rate of raptor flying over). Several observations showed that refuelling on the beach, which presented the most favourable feeding conditions and allowed high rates of body mass gain, was metabolically limited. The total time devoted to foraging was independent of day length, and additional food (mealworms) offered in bowls was completely ignored, an indication that reduced foraging effort would not improve net energy gain within the physiological capacity. In contrast, Wheatears responded strongly to additional food supplied in the poorer grassland habitat. Although this strongly suggests that refuelling is limited by the amount of food available and the costs of obtaining it, foraging times were the same as on the beach. In grassland, the behaviour pattern of birds refuelling was probably distorted by a high proportion of transient and exploring individuals. Therefore, knowledge about foraging ecology and the response to additional food improves the value of the foraging time parameter in considerations of refuelling limitations.

Diarrhetic shellfish toxicity in relation to the abundance of Dinophysis spp. in the German Bight near Helgoland

Diarrhetic shellfish toxicity is caused by the accumulation of okadaic acid and its deriv- atives, which are produced by particular species of Dinophysis Ehrenberg 1839 and Prorocentrum Ehrenberg 1833 (Dinoflagellata). In the German Bight (North Sea) around the island of Helgoland, 4 toxic Dinophysis species occur, of which 2 exhibited successive biomass maxima in summer 2000 (D. norvegica Claparede et Lachmann 1859 with cell concentrations of max. 400 cell l -1 and D. acumi- nata Claparede et Lachmann 1859 with max. cell concentrations of over 4000 cells l -1 ). In contrast to findings in other marine areas, toxicity of Mytilus edulis Linne 1758 could be clearly attributed to the observed increases in cell abundances of both species. In several Mytilus samples toxin concentra- tions (max. 460 ng diarrhetic shellfish poisoning (DSP) toxins g -1 hepatopancreas) were in a range which is considered dangerous for human consumption. While mussel toxicity coincided with concentration increases of both Dinophysis species, toxicity of the particulate substance in the water (max. 26 ng l -1 ) could be detected only during cell concentration maxima of D. acuminata. Mussel toxicity lasted 3 wk after the end of the D. acuminata bloom, and this is attributed to extended toxicity of decaying Dinophysis cells and detritus. Elevated summer temperatures and low silicate concen- trations evidently supported the development of high concentrations of D. acuminata.

Molecular analyses elucidate the taxonomy of fully corticated, nonspiny species of Ceramium (Ceramiaceae, Rhodophyta) in the British Isles

Four fully corticated nonspiny species of Ceramium are currently recognized in the British Isles, all formerly confused under the illegitimate name Ceramium rubrum (Hudson) C. Agardh. One of these species was known briefly as C. nodulosum (Lightfoot) Ducluzeau but, in 1996, P.C. Silva and others [Univ. Calif. Publ. Bot. 79] showed that this is a later homonym of C. nodulosum de Candolle and advocated conserving C. rubrum with a neotype. As an alternative to this, we investigated whether the name C. virgatum Roth 1797 might be available for this species. The aim of the present study was to typify C. virgatum, in the context of better characterizing this and the other fully corticated species of Ceramium that occur in the British Isles, by analysis of plastid DNA (cpDNA) restriction fragment length polymorphism (RFLP) or rbcL sequences (or both) of each species from various sites, including their type localities. The lectotype of C. virgatum is Roth's illustration of a Ceramium specimen from Eckwarden, North Sea, which could represent any member of the ‘C. rubrum’ group. Material resembling Roth's from the North Sea island of Helgoland is here designated as an epitype of C. virgatum. Its rbcL sequence was aligned with sequences of al1 C. rubrum-like species in the British Isles, viz. C. secundatum, C. botryocarpum, C. pallidum and ‘C. nodulosum’. The Helgoland material was clearly conspecific with the alga previously identified as C. nodulosum from Ireland (0.08% rbcL divergence, compared to a minimum between-species divergence of 1.8%). We therefore suggest that the name C. virgatum Roth should be employed for this species. Each of the four fully corticated species can be identified by morphological features, in particular the number of axial segments between branches. Phylogenetic analyses of rbcL sequences and cpDNA RFLP data showed C. pallidum to be basal among the North Atlantic C. rubrum-like species and indicated a close relationship between C. secundatum and C. botryocarpum.

Long-term effects of ultraviolet radiation on growth and photosynthetic performance of polar and cold-temperate macroalgae

Long-term effects of artificial ultraviolet radiation (UV) and natural solar radiation on growth and photosynthetic activity, as measured by chlorophyll fluorescence, were investigated in 13 different polar and cold-temperate macroalgal species. Isolates of five different species from the Arctic and Antarctic were exposed to different light treatments of photosynthetically active radiation (PAR), PAR+UVA and PAR+UVA+UVB. Eight different species collected on the island of Helgoland, North Sea, Germany, were studied in the laboratory and under natural solar radiation conditions. Increase in fresh weight and changes in photosynthetic performance were monitored over a period of 3–4 weeks. The sublittoral polar species, particularly the Antarctic red algal species Gymnogongrus antarcticus and G. turquetii, the Arctic cold-temperate brown alga Alaria esculenta and, very drastically, the Arctic-endemic Laminaria solidungula, exhibited strong inhibiting effects of artificial UVB radiation on growth. In the cold-temperate sublittoral growth of the red algae Phycodrys rubens and, to a lesser extend, Membranoptera alata was substantially inhibited by UV radiation. In contrast, eulittoral species, e.g. Fucus serratus, did not show any differences in growth with respect to artificial irradiation conditions, with or without UV radiation. In the laboratory, some individuals of the green alga Codium fragile exhibited strong morphological changes of the whole thallus, particularly under UVB exposure. In the experimental outdoor set up, growth of most of the algal species was already inhibited by the full solar UV waveband, but, apart from Polyides rotundus, no additional UVB effect could be detected. Changes of in vivo fluorescence were not always consistent with the measurable changes in growth rate, indicating that physiological processes leading to an inhibition of growth may act independently of changes in photosynthetic activity. For the polar species, a general correlation between the natural vertical distribution in the field and the individual sensitivity towards UV radiation was indicated, while for eulittoral species from Helgoland no clear relationship was found. The obtained results show that measuring growth is a good ecological parameter to monitor long-term effects of UV radiation on single macroalgal species and the possible resulting changes of whole algal communities in coastal ecosystems.

Lead in sediments and suspended particulate matter of the German Bight: natural versus anthropogenic origin

Sediments (568) and suspended particulate matter (SPM, 302 samples) of the southern German Bight and the adjacent tidal flat areas were analysed for selected major elements (Al, Fe, K), trace metals (Mn, Pb), and 206Pb/ 207Pb ratios using XRF, ICP–OES, ICP–MS. For selected samples a leaching procedure with 1 M HCl was used to estimate the Pb fraction associated with labile phases (e.g. Mn/Fe-oxihydroxide coatings) in contrast to the resistant mineral matrix. Enrichment factors versus average shale (EFS) reveal elevated Pb contents for all investigated sediments and SPM in the following order: Holocene tidal flat sediments (HTF, human-unaffected) <recent tidal flat sediments (RTF) <Helgoland Island mud hole sediments (MH) <nearshore SPM (SPM concentration>5 mg l −1) < offhore SPM (<5 mg l −1). Besides pollution, RTF contain elevated amounts of natural Pb-rich materials (K-feldspars and heavy minerals) due to a man-made high-energy environment (dike building) in comparison to HTF. 206Pb/ 207Pb ratios of RTF (1.192±0.019) are similar to the local geogenic background, determined from HTF (1.207±0.008). In contrast, Pb isotope ratios of nearshore SPM (1.172±0.007) and offshore SPM (1.166±0.012) show a distinct shift towards the anthropogenic/atmospheric signal of 1.11–1.14. This difference between RTF and SPM supports the assumption of low deposition rates of fine material in the intertidal systems. As the 206Pb/ 207Pb ratios of SPM do not reach the pure anthropogenic signal, the adsorbed Pb fraction was examined (leaching). However, the leachates also contained large amounts of geogenic Pb (SPM ≈40%, recent sediments ≈60%). The authors assume that the uptake of natural Pb occurs in nearshore waters, presumably in the turbid intertidal systems. Possible sources for dissolved Pb are mobilisation during weathering (geogenic signal) and dissolution of oxihydroxide coatings with subsequent release from porewaters, and unspecific riverine input. Comparatively small parts of SPM leave the coastal water mass and reach the open North Sea. This process therefore leads to a decontamination of the tidal flat sediments. Due to more pronounced atmospheric input, the offshore SPM becomes enriched in anthropogenic Pb as indicated by decreasing 206Pb/ 207Pb ratios with increasing distance from the coast.

Wavelength-dependent induction of UV-absorbing mycosporine-like amino acids in the red alga Chondrus crispus under natural solar radiation

Polychromatic response spectra for the induction of UV absorbing mycosporine-like amino acids (MAAs) were calculated after exposing small thalli of the red alga Chondrus crispus under various cut-off filters to natural solar radiation on the North Sea island Helgoland, Germany. The laboratory-grown specimens typically contain only traces of palythine and synthesise five different MAAs rapidly and in high concentrations after being transplanted into shallow water. The resulting qualitative and quantitative patterns of MAA induction differed markedly with respect to spectral distribution. Furthermore, the wavebands effective for MAA induction vary within the MAA. UV-B radiation had a negative effect on the accumulation of the major MAAs shinorine ( λ max=334 nm) and palythine ( λ max=320 nm), while short wavelength UV-A exhibits the highest quantum efficiency on their synthesis. In contrast, the synthesis of asterina-330 ( λ max=330 nm), palythinol ( λ max=332 nm) and palythene ( λ max=360 nm) was mainly induced by UV-B radiation. Whether the synthesis of shinorine and palythine is induced by a photoreceptor with an absorption maximum in the short wavelength UV-A and whether a second photoreceptor absorbing UV-B radiation is responsible for the induction of asterina-330, palythinol and palythene remains to be studied. Our results show that C. crispus has a high capacity to adapt flexibly the qualitative and quantitative MAA concentration to the prevailing spectral distribution of irradiance. On one hand, this is regarded as an important aspect with respect to the acclimation of algae to increasing UV-B irradiance in the context of ongoing depletion of stratospheric ozone. On the other hand, the experiment demonstrates that UV-A irradiance is more important for the induction of the major MAAs shinorine and palythine than UV-B.

Stopover behaviour and departure decision of northern wheatears, Oenanthe oenanthe , facing different onward non-stop flight distances

On the small North Sea island Helgoland (54°11′ N, 07°55′ E) we studied the stopover ecology of two subspecies of northern wheatear, Oenanthe oenanthe, during spring migration. Birds heading for Scandinavia (O. o. oenanthe) face only short flights across an ecological barrier (50–500 km) whereas those originating from Greenland and Iceland (O. o. leucorhoa) have to cover between 1,000 and 2,500 km in the impending flight. Colour-ringed individuals showed that 90% of Scandinavian birds left on the day of ringing while 40% (males) and 30% (females) of Greenland/Icelandic birds stayed at least 1 night. The birds who remained were thus mostly O. o. leucorhoa. They often established desirable feeding territories on the beach and had a high rate of body mass increase (1.7 g/day). However, subspecies did not differ in habitat choice and in foraging effort, but O. o. leucorhoa had a higher success rate in pecking. Departure decisions were analysed by comparing (a) conditions on the day of ringing between departing and staying birds and (b) for birds staying between the day of departure and the preceding day. The factors that were probably important in the decision to depart differed between subspecies. In O. o. leucorhoa, few birds departed with bad or deteriorating weather conditions (tailwind component, cloud cover), whereas departures of O. o. oenanthe seemed to be little affected by those factors. A few O. o. oenanthe stayed early in the spring migration season and/or had low fat reserves. Interference during foraging seemed to play a role because both subspecies tended to leave when the densities of northern wheatears were high. Other factors related to refuelling conditions (food supply, foraging effort, predation risk) failed to show differences between staying and departing individuals. In summary, almost all Scandinavian birds departed quickly and irrespective of refuelling and weather conditions, whereas many (but not all) Greenland/Icelandic birds seemed to prepare for a long-distance flight and carefully adjusted departure to weather conditions. The observed differences in stopover behaviour and departure decisions in the two subspecies of northern wheatear indicate that the distance to the next stopover site or to the goal area has to be considered when applying optimal migration models.

Large gulls as predators of passerine landbirds migrating across the southeastern North Sea

The predation by large gulls on passerines migrating across the southeastern North Sea was studied on the offshore island Helgoland throughout 1999; 15,307 pellets of Herring Gull Larus argentatus and Great Black-backed Gull L. marinus were examined. The main prey was fish and crustaceans, but during migratory seasons of passerines (March to May, August to November) up to 7% of the pellets contained remnants of passerines (mainly thrushes Turdus spp. and Starlings Sturnus vulgaris, but few species of &lt;50 g body mass). For half-month periods, the number of pellets containing passerines correlated with the number of passerines stopping over on Helgoland for both size categories of &lt;50 g and &gt;50 g. Pellets containing passerines were mainly found during weather conditions favourable for migration, when many birds were aloft, rather than during adverse conditions. Based on the number of large gulls present, an estimated 5,200 passerines might have fallen victim to gulls during the year. Although some passerines may be scavenged rather than captured, gulls must be important potential predators for passerines migrating across the sea.

Helgoland (Deutschland): Hämogenetische Untersuchung einer Inselpopulation

24 haemogenetic markers (5 erythrocyte antigenes, 6 polymorphisms of serum proteins, 12 polymorphisms of red cell enzymes) had been studied in up to 80 individuals from the island of Helgoland (Germany). The cluster analysis separates clearly the Helgoland sample from the neighbouring populations as well as from European standard data. This special position is interpreted partly by genetic peculiarities developed in the course of time, partly as a consequence of genetic drift.

On the current and possible future status of the neustonic isopod Idotea metallica Bosc in the North Sea: a laboratory study

In the 1990s, a period of extraordinarily mild winter temperatures in the German Bight (North Sea), the oceanic, neustonic isopod Idotea metallica Bosc was found for the first time off the island of Helgoland. The species was recorded in subsequent summer periods, reproducing successfully in the area, while its whereabouts in winter remained uncertain. The question arises whether a continuing increase in mean winter water temperature, as predicted in most scenarios on future climate, might enable I. metallica to overwinter in the North Sea and to become a permanent resident there. Experiments on laboratory-cultured I. metallica were performed for the first time. Population dynamics was studied at different temperatures in microcosms. Furthermore, the temperature effects on reproductive output, mortality and duration of embryonic development were studied in individually reared animals. The results suggest that at current temperature conditions (mean winter water temperature of about 5°C) I. metallica is unable to overwinter in the German Bight, and that even an increase to about 8°C probably would not change this situation. The recently observed summer populations of the species in the German Bight obviously originate from individuals introduced each year anew by water currents from the Atlantic Ocean. Nevertheless, I. metallica may be useful as a sensitive indicator: in a warming North Sea the species may become a regular summer immigrant, developing more and more conspicuous populations in this area as the annual period with water temperature above the critical level (13°C) for reproduction extends.

Microbial diversity of cultivatable bacteria associated with the North Sea bryozoan Flustra foliacea

The microbial diversity of cultivatable bacteria associated with the bryozoan species Flustra foliacea from the North Sea was investigated by a molecular approach. Amplified ribosomal RNA restriction analyses (ARDRA) and 16S rDNA partial sequence analysis revealed differences in the composition of cultivatable bacteria populations from single bryozoan colonies collected from two different sampling sites in the North Sea as well from one site taken at different points in time. Whereas gamma-Proteobacteria identified as Shewanella frigidimarina, Pseudoalteromonas ssp. and Psycbrobacter ssp. were predominant on samples of Flustra I (taken near the island of Helgoland), most bacteria isolated from Flustra II, originating from the Steingrund, could be affiliated to Gram-positive taxa. Survey of the bryozoan samples from the latter site in February 2000 led to the detection of a phylogenetically mixed bacterial population, consisting of gamma-, and alpha-Proteobacteria and Gram-positive bacteria with low and high GC-content (Flustra III). As these bacteria are among the most widely isolated organisms from the marine environment, it may be concluded that the bryozoan Flustra foliacea accepts colonization of surfaces by bacteria which are common inhabitants of the marine environment and which may have been transferred into this environment from terrestrial sites.

THE TYPE SPECIES OF CERAMIUM (RHODOPHYTA), CERAMIUM VIRGATUM ROTH: TYPIFICATION AND PHYLOGENY

The type species of Ceramium is Ceramium virgatum Roth (1797, Cat. Bot I: 148, pl. VIII, fig. 1). This has been treated as a probable synonym of Ceramium nodulosum (Lightfoot) Ducluzeau, one of the species formerly confused under the illegitimate name Ceramium rubrum (Hudson) C. Agardh. However, in 1996 Silva showed that C. nodulosum (Lightfoot) Ducluzeau is a later homonym of C. nodulosum de Candolle 1805, and advocated conserving C. rubrum with a neotype. As an alternative to this, we investigated whether the name C. virgatum might be available for this species. The lectotype of C. virgatum is Roth's illustration of a much‐branched, fully corticate, Ceramium specimen from Eckwarden, North Sea, which could represent any member of the ‘C. rubrum’ group. We obtained material resembling Roth's, from the North Sea island of Helgoland, as a potential epitype. Its rbcL sequence was aligned with sequences of all C. rubrum‐like species in the British Isles, i.e. C. secundatum, C. botryocarpum, C. pallidum and ‘C. nodulosum’. The Helgoland material was clearly conspecific with ‘C. nodulosum’ from Ireland (0.08% divergence). We therefore suggest that the name C. virgatum Roth should be employed for this species. Phylogenetic analyses of these sequences aligned with various representatives of the tribe Ceramieae, placed the North Atlantic C. rubrum‐like species in two well‐supported clades. In one of these, C. virgatum is basal to C. secundatum and C. botryocarpum. The other clade consists of C. pallidum and a partly ecorticate species resembling C. diaphanum.