Jan Rines

Systematics of Chaetocerotaceae (Bacillariophyceae). I. A phylogenetic analysis of the family

In order to construct a model of evolutionary relationships within the diatom family Chaetocerotaceae, 37 species of Chaetoceros Ehrenberg, representing all subgenera and 21 of 22 subgeneric sections of the genus, plus three Bacteriastrum Shadbolt species, representing both of its subgeneric sections, were subjected to cladistic analysis. One species each of Eucampia Ehrenberg, Cerataulina Peragallo, Hemiau‐lus Ehrenberg, Attheya West and Gonioceros H. & M. Peragallo were used as outgroups. A matrix of 65 binary and multistate morphological characters was constructed, with data being gathered from original observation of material in the light and electron microscopes, and from the published literature. The analysis yielded 36 most‐parsimonious cladograms of 316 steps; incongruence between trees is largely restricted to some taxa representing undersampled sections of Chaetoceros subg. Hyalochaete. The robustness of this hypothesis was examined in several ways. To assess the effect of character weighting, the bootstrap was used to randomly weight characters. The parsimony criterion was relaxed via a decay index, and finally, the tree length was compared to that of trees randomly generated from the data matrix. The majority of investigated species of Chaetoceros subg. Phaeoceros, Chaetoceros subg. Hyalochaete and Bacteriastrum appear to belong to a continuous grade, rather than comprising individual clades. Chaetoceros is paraphyletic. Thus, the traditional classification does not accurately reflect the hypothesized phylogenetic relationships of this family.

Haslea ostrearia-like Diatoms: Biodiversity out of the Blue

Abstract Diatoms are usually referred to as golden-brown microalgae, due to the colour of their plastids and to their pigment composition, mainly carotenoids (fucoxanthin, diadinoxanthin, diatoxanthin), which mask chlorophylls a and c . The species Haslea ostrearia Gaillon/Bory (Simonsen) appears unique because of its extraplastidial bluish colour, a consequence of the presence of a water-soluble blue pigment at cell apices, marennine. When released in seawater, marennine can be fixed on gills of oysters and other bivalves, which turn green. This greening phenomenon is economically exploited in Southwestern France, as it gives an added value to oysters. For decades, this singularity ascribed a worldwide distribution to H. ostrearia , first as Vibrio ostrearius , then Navicula ostrearia , last as H. ostrearia , when the genus Haslea was proposed by R. Simonsen (1974) . Indeed, this ‘birthmark’ (presence of blue apices) made H. ostrearia easily recognisable without further scrutiny and identification of the microalga as well as its presence easily deduced from the greening of bivalves. Consequently, the widely admitted cosmopolitan character of H. ostrearia has only been questioned recently, following the discovery in 2008, of a new species of blue diatom in the Black Sea, Haslea karadagensis . The biodiversity of blue diatoms suddenly increased with the finding of other blue species in the Mediterranean Sea, the Canary Islands, etc., the taxonomic characterization of which is in progress. This review thus focuses on the unsuspected biodiversity of blue diatoms within the genus Haslea . Methods for species determination (morphometrics, chemotaxonomy, genomics), as well as a new species, are presented and discussed.

Chaetoceros phuketensissp. nov. (Bacillariophyceae): a new species from the Andaman Sea

Over 400 species of Chaetoceros Ehrenberg have been described since the genus was created in 1844, making this one of the most species‐rich genera of marine planktonic diatoms. Although Chaetoceros is cosmopolitan in distribution, the temperate north Atlantic taxa are best known. Examination of material from tropical seas suggests that there are numerous Chaetoceros endemic to these biogeographic regions, which await formal description. Chaetoceros phuketen‐sis sp. nov. is described from the Andaman Sea, in the tropical Indian Ocean. It possesses several unusual morphological characteristics not found in temperate taxa, including multiple central processes on terminal valves, vermiform chloroplasts and large size. It is most similar to Chaetoceros buceros Karsten and Chaetoceros bermejensis Hernàndez‐Becerril, which also inhabit tropical seas. These taxa are not easily accommodated in the traditional classification scheme, which was based on turn‐of‐the‐century knowledge of north Atlantic taxa. Approaches for classifying these unusual species include modifications of the extant scheme and creation of a new scheme based on phylogenetic principles.

A biological source of bubbles in sandy marine sediments

Gas in sediments, even in small quantities, will modify the propagation and scattering of sound. Shallow water littoral environments are often sufficiently well lit by sunlight to support healthy populations of benthic and epibenthic marine microalgae. Photosynthesis in marine algae produces oxygen. Oxygen saturation levels as high as 600% have been measured in the pore water of a sandy sediment at 1 mm depth, decreasing to 100% saturation at ca. 4.5 mm. Bioturbation and physical processes routinely mix materials at the surface of the seabed, including algae, to depths of at least a few cm. Mixing times and depths vary with the sediment type and the species and abundance of organisms present, but time scales of minutes to hours are common. While light is rapidly attenuated with depth in sand, measurements show that it can penetrate to depths of a few mm. Physical and biological mechanisms are suggested which could produce gas bubbles in oxygen saturated pore water. Laboratory measurements of sound scattering from marine algae on a sand surface suggest a possible method for in situ bubble detection in shallow marine environments. [Work supported by ONR.]

Biological thin layers: history, ecological significance and consequences to oceanographic sensing systems

Thin layers are water column structures that contain concentrations of organisms (or particles) that occur over very small vertical scales (a few meters or less), but with large horizontal scales (e.g. kilometers). Thin layers are now known to be common phenomenon in a wide variety of environments and can be a critical componant in marine ecosystem dynamics and functioning. While knowledge about their dynamics is important to our basic understanding of oceanic processes, thin layers can have significant impacts on both oceanographic and defense related sensing systems, e.g. thin layers can affect underwater visibility, imaging, vulnerability, communication and remote sensing for both optical and acoustic instrumentation. This paper will review the history of thin layers research, their ecological significance, innovations in oceanographic instrumentation and sampling methodologies used in their study, and the consequences of their occurence to oceanographic sensing systems.

Modeling Analysis of Physical Transport and Swimming Behaviors Determining Plankton Distributions

An experimental study and modeling analysis was performed to determine the relative importance of physical transport versus swimming behavior in determining the distribution of zooplankton and their retention in patches of high phytoplankton density. The experiment involved establishing, maintaining and sampling a natural plankton patch in a ∼1-km long tank (3.3 m deep by 7.3 m wide). Natural plankton containing a mixture of Chesapeake Bay algal species dominated by the calanoid copepod Acartia hudsonica were inoculated into the lighted center of the tank within a plastic bag such that the plankton patch was held in place. The patch was grown (via lighting and nutrient additions) to a relatively high density as compared to the surrounding water. After balancing the water density throughout the tank, the patch was released by removing the plastic bag. The physical regime was such that the patch was sheared. Copepod distributions were sampled and modeled, including physical transport and various swimming behaviors, to determine if the observed movements could be accounted for purely by physical transport, or whether the animals needed to swim either vertically or horizontally to account for the changing densilies in space and lime. Modeling results indicated that younger copepod stages moved purely by physical transport and randomly-directed swimming, but that there was evidence of directed movement by older copepods. Vertical migration behavior, coupled with physical transport and randomized foraging behavior, was sufficient to explain the distribution of older stage copepods; oriented horizontal swimming behaviors were not needed to account for distributions. Such directed movements, coupled with physical transport, are important determinants of plankton distributions, both for holo-zooplankton and larval fishes. Additional species and conditions need to be evaluated to fully understand the roles of directed swimming behaviors and physical transport in determining plankton distributions.