Volume 55, Issue 1

This paper is written in honour of the influential career of Professor T.J. Smayda. It celebrates the brief, but productive, period in which we collaborated on the formulation of the principles and mechanisms of community assembly in plankton. The topics considered then provide the structure of the present paper – the origin of communities (nascence), the common and differential requirements of phytoplankton species that might affect their selection, the general and specialist adaptive traits that differentiate their performances and their relative successes, and the sensitivity of performances to sub-ideal or hostile environmental conditions. In all these instances, it is the reactivity of the net dynamic responses of the species present to imposed environmental variations that shapes the structure of the assemblage and the composition of the community. These are the high-level properties that emerge from the behaviour of low-level components. The patterns that emerge at the community level – selection by performance or competition, dominance and temporal succession – are qualitatively predictable and, at the assemblage level, are amenable to quantitative modelling. In turn, it is theoretically possible to make deductions about the likelihood of biological events that involve species occurring in abundances sufficient to affect water quality and/or constitute risks to human health (harmful algal blooms).

The harmful dinoflagellate Prorocentrum minimum reportedly has variable toxicity to grazing animals. We used the bay scallop Argopecten irradians irradians as a bioassay organism to compare expression of harmful effects of P. minimum cultures in growth or senescent phases. The non-toxic alga Rhodomonas sp. was used as a control. Exposure to both types of P. minimum cultures decreased the degree of shell opening, amount of biodeposits produced, motility and byssal-thread attachment. As P. minimum cultures approached senescence, effects became more severe, and mortality increased to 15% in scallops exposed to senescent P. minimum . Pathological effects of P. minimum on scallops included derangements of scallop digestive tubules and the adductor muscles, and abnormal hemocyte distributions, which were more severe in scallops exposed to senescent cultures. These findings help to explain the variable toxicity of P. minimum to scallops and other bivalves reported in the literature. Further, these findings demonstrate that the definition of a “harmful algal bloom” should probably be expanded to include physiological status along with identity and abundance of a phytoplankton species.

Shorebirds, including sanderlings ( Calidris alba ) and ruddy turnstones ( Arenaria interpres ), were observed scavenging beached fish, such as thread herring ( Opisthonema oglinum ), scaled sardine ( Harengula jaguana ) and mullet ( Mugil spp.) killed during a 2005 Karenia brevis red tide along the central west coast of Florida. Brevetoxin concentrations in dead fish tissues were analyzed to determine the potential exposure risk to scavenging shorebirds. This component of brevetoxin cycling in the food web has not previously been explored and the risks or benefits of this behavior for shorebirds are not currently understood. Toxin levels in freshly dead fish tissues ranged from 32 to 95,753 ng PbTx g -1 . Brevetoxins in shorebird livers were also confirmed (26–1313 ng PbTx g -1 ) in dead birds collected opportunistically from local beaches and rehabilitation centers during the red tide event, suggesting that brevetoxin exposure is a risk factor for mortality. These findings underscore the need to assess the ecological impacts of K. brevis blooms on Florida’s migratory and resident shorebird populations.

In the period 2001–2003, I quantitatively explored the importance of mixotrophic and heterotrophic dinoflagellates in four eutrophic gulfs on the Greek coastline of the Aegean Sea, eastern Mediterranean. Phytoplankton analysis (250 samples, 401 species) focused on determinations of cell abundance and carbon biomass of diatoms, dinoflagellates (autotrophic, mixotrophic, heterotrophic), and coccolithophores. Among the 177 dinoflagellates, 145 autotrophic, 18 mixotrophic, and 14 heterotrophic species were identified comprising up to 18%, 3%, and 1% of total phytoplankton cell abundance, respectively. Analysis of total carbon biomass contributions among taxa showed that the heterotrophic dinoflagellate population contributed the highest carbon proportion (65%) to the stocks of phytoplankton community in contrast to the low contributions of the autotrophic (14%) and mixotrophic (1%) dinoflagellate species. One heterotrophic and 11 mixotrophic species were harmful algae. This major contribution of heterotrophic species to total carbon biomass may affect the concepts of trophodynamics and food web structure. Seasonal and regional distributions of heterotrophic and mixotrophic dinoflagellates are considered.

Intertidal pools represent restricted habitats for macroalgal assemblages, and their structure is determined by physical and biotic factors. The establishment of the exotic oyster Crassostrea gigas on the north Patagonian Atlantic coast led to the formation of intertidal pools; these provide habitats for macroalgal settlement. We aimed to determine the composition, distribution and abundance of the macroalgal assemblage inhabiting these pools, and to establish the structuring variables. Several biotic and abiotic variables were evaluated in 36 pools in winter and summer. Correlations were calculated and permutation analysis of variance and constrained redundancy analysis were conducted to determine the structuring variables. Unlike other Patagonian coasts, richness was low and pools were characterized by a dominance of red algae. Richness was higher in winter, while diversity was lower because of the dominance of Polysiphonia abscissa , which had the highest percentage of occurrence. Temperature was a putative factor determining seasonal richness and diversity. Elevation and surface area of the pools were structuring factors for assemblage biomass. We demonstrated distinct assemblage dynamics. Polysiphonia abscissa developed large populations in winter, which declined towards the summer, while Gelidium maggsiae and Gelidiella calcicola formed dense turfs during summer stress.

Clipperton Island is a small French coral atoll in the eastern Pacific Ocean, which has been rarely investigated because of its remote location and difficult access. There is little scientific information on this ecosystem and only a few microalgae have been reported from the lagoon. To date, only one dinoflagellate taxon, Peridiniopsis cristata , is known to inhabit the lagoon. During an expedition in 2005 to study the lagoon and the surrounding oceanic waters of Clipperton Island, a further investigation of the lagoon phytoplankton was undertaken. In addition to P. cristata, which was still abundant in the upper water layer, two other thecate dinoflagellates were recorded. One dinoflagellate was identified as Durinskia baltica , while the other had the same thecal plate arrangement as P. cristata but was slightly smaller, (27) 30–40 μm long, 26–32 μm wide, and its plates were unornamented and devoid of prominent lists. Hence, the latter taxon is described as P. cristata var. tubulifera since it represents an extreme variation in the ornamentation of the nominate variety. This study provides a description and detailed illustrations of the three taxa found in this peculiar tropical marine ecosystem.

Coastal phytoplankton samples were analyzed from two locations in the tropical Mexican Pacific Ocean. Three solitary, presumably epipsammic diatom species were studied in detail: Aulacodiscus petersii , A. scaber , and a new species of Cerataulus , C. simsae . Most morphological features previously described for A. petersii and A . scaber were also found in this study; however, we found great variation in the external tube of the rimoportulae in terms of size and complexity. Although C. simsae was less common, it also showed significant size and shape variation. The species has slightly undulated frustules in girdle view, with elliptical to circular valves; it also has two opposite, marginal ocelli that are not prominent, but rather almost flush with the valve face. The valves are usually covered by granules (marginal granules have a short peduncle) of different sizes that mask the areolae. A marginal ring of rimoportulae, with no large protrusion to the outside, but rather small “knobs”, was found in valves of the species. Cerataulus simsae is probably closely related to C . californicus . Cerataulus should be revised because its generic circumscription and relationships are unclear.

For the first time the subarctic northwestern Atlantic, we examined variation in rhodolith ( Lithothamnion glaciale ) morphology and biogenic potential in two large (>500 m 2 ) rhodolith beds we discovered recently between the depths of 5–25 m off St. Philip’s and Holyrood, Newfoundland and Labrador. Rhodoliths at St. Philip’s were >50% larger and contained 7% more internal space in deep (15–17 m) than shallow (8–10 m) water, whereas shallow rhodoliths were >180% larger at Holyrood than at St. Philip’s. Rhodoliths were predominantly spheroidal and compact at St. Philip’s and platy or bladed at Holyrood. Shallow rhodoliths varied in length from 41.1–114.6 mm at St. Philip’s and 61.3–189.1 mm at Holyrood. Rhodolith density was similar between beds (858.1–938.9 individuals m -2 ) although biomass was significantly higher at Holyrood than St. Philip’s (25.3 versus 19.4 kg m -2 ). There was a strong positive relationship (R2>0.93) between rhodolith volume and dry weight in both beds. Invertebrates associated with shallow rhodoliths belonging to the taxonomic groups Asteroidea, Echinoidea, Ophiuroidea, Bivalvia, Gastropoda, Polyplacophora, Crustacea, and Annelida were present at both sites, although they varied in terms of size, density, and biomass. Brittle stars ( Ophiopholis aculeata ) and chitons ( Tonicella marmorea ) accounted for at least 82% (up to 2026.7 individuals m -2 ) of total numbers of invertebrates in each bed. Larger rhodoliths appeared to facilitate reproduction and feeding in dominant fish and invertebrate species. Differences in hydrodynamic conditions within and between beds may have contributed to these patterns.

The algae of El Salvador have received limited attention. We combined collections from the mangroves of El Salvador and neighboring southern Mexico, and used culture studies and molecular analysis to gain insights into the diversity in this poorly explored region. Bostrychia montagnei , Caloglossa apomeiotica , and Caloglossa ogasawaraensis were newly recorded in El Salvador. Bostrychia montagnei has not been reported from the Pacific Americas before. B. montagnei normally produced axial cells with two-tier cells, typical of the species, but sometimes a series of axial cells had three-tier cells. This was a significant tier cell number variation not previously seen in Bostrychia species. Bostrychia montagnei had a Polysiphonia -type sexual life history with both unisexual and bisexual gametophytes. Caloglossa apomeiotica isolates in culture from El Salvador and Chiapas, Mexico, either had a normal sexual life history or asexual recycling of tetrasporophytes. Those found in El Salvador were the first record of C. apomeiotica south of Jalisco, Mexico, a distance of 1200 km. Four strains isolated from El Salvador and Chiapas, Mexico, which were morphologically part of the Caloglossa leprieurii sensu lato lineage, were analyzed; however, they were not closely related to any named species, indicating that this is a new species that will require further study.

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No abstract available