Agneta Persson

Life in Ballast Tanks

The abundance and diversity of species in ballast water, a recognised vector for the accidental introduction of nonindigenous organisms, has been examined through many studies around the world over the last 25 years. The results of European research activities are summarised in this contribution by outlining the objectives of some of these studies, and by focusing on the diversity of taxa determined from ballast water and tank sediment samples. In total 1508 samples (1219 ballast water, 289 tank sediment) were collected on 550 ships. A total of 990 taxa were identified during the 14 European shipping studies. The diversity of species found included bacteria, fungi, protozoans, algae, invertebrates of different life stages including resting stages, and fishes with a body length up to 15 cm. Crustacean, molluscan and polychaete invertebrates and algae form the majority of species found.

Dinoflagellate Cysts in Recent Sediments from the West Coast of Sweden

Abstract This is the first study of dinoflagellate cysts in recent coastal sediments from the Swedish west coast. Sediments from 19 sites were investigated. Fifty-four types of cysts were encountered, of these 40 were identified to species level, representing 13 genera. The most common species were those of Lingulodinium polyedrum, Protoceratium reticulatum, Scrippsiella trochoidea, Pentapharsodinium dalei and Gonyaulax cf. spinifera. Cysts of the potentially toxic species Alexandrium minutum and Alexandrium tamarense were widely distributed as well as Gymnodinium nolleri, the non-toxic G. catenatum-like microreticulate cyst found in Northern Europe. Nine of the species found in this survey have not previously been reported from Sweden: Diplopelta parva, D. symmetrica, Diplopsalopsis latipeltata, Diplopsalis lebourae, Protoperidinium americanum, P. avellana, P. divaricatum, P. nudum and P. stellatum.

Effects of UV-B radiation on synthesis of mycosporine-like amino acid and growth in Heterocapsa triquetra (Dinophyceae)

Abstract Unialgal cultures of the dinoflagellate Heterocapsa triquetra (Ehrenberg) Stein were exposed to artificial UV-B radiation and the growth and synthesis of mycosporine-like amino acids (MAAs) were compared with cultures shielded from UV-B radiation by sharp cut-off films. The UV-B radiation did not affect the growth (the increase in total cell volume of the culture) but resulted in an increase in the size of the individual cells and synthesis of MAAs. The synthesis of MAAs during UV-B radiation was synchronised with the cell cycle, being maximal during periods of increases in cell size without division. The absorbance spectra of the MAAs during UV-B radiation changed, showing higher absorption in the UV-B range as compared to the controls.

Impact of grazing and bioturbation of marine benthic deposit feeders on dinoflagellate cysts

Abstract The impact of benthic deposit feeders on marine dinoflagellate cysts was studied by adding a concentrated natural Swedish cyst assemblage to sediment with different deposit feeders in replicate 4-l aquaria. The deposit feeders used were the bivalve Abra nitida, the echinoderm Amphiura filiformis, and the polychaetes Melinna cristata and Nereis diversicolor. These species occur naturally near the Swedish west coast and were selected to represent different ways of feeding. The results showed a significant relative decrease of unfossilizable cyst species; whereas, the common fossilizable species Lingulodinium polyedrum significantly increased in the cyst assemblage after grazing. This work suggests that differences in dinoflagellate cyst compositions can in part be caused by different animal grazing behaviors.

The Eastern Mudsnail, Ilyanassa obsoleta, Actively Forages For, Consumes, And Digests Cysts Of The Dinoflagellate, Scrippsiella lachrymosa

The Eastern mudsnail, Ilyanassa obsoleta, was attracted to, consumed, and digested resting cysts of the dinoflagellate Scrippsiella lachrymosa when cysts were presented in grazing experiments. Twenty snails were observed individually for one hour in petri dishes divided into four parts wherein cysts were present in one quadrant, sediment particles of the same size range were in another quadrant, and two quadrants were free of particles. Actively foraging snails were nearly twice as likely to be found in quadrants containing S. lachrymosa cysts as in the other quadrants until cysts were consumed. Microscope observations of fecal pellets from snails feeding on cysts revealed digestive destruction of the cysts. These findings indicate that deposit-feeding grazers can actively seek dinoflagellate cysts as a food item, thereby influencing distribution of cysts and subsequent germination of dinoflagellate vegetative cells.

Differences in pigmentation between life cycle stages in Scrippsiella lachrymosa (dinophyceae).

Various life cycle stages of cyst‐producing dinoflagellates often appear differently colored under the microscope; gametes appear paler while zygotes are darker in comparison to vegetative cells. To compare physiological and photochemical competency, the pigment composition of discrete life cycle stages was determined for the common resting cyst‐producing dinoflagellate Scrippsiella lachrymosa. Vegetative cells had the highest cellular pigment content (25.2 ± 0.5 pg · cell−1), whereas gamete pigment content was 22% lower. The pigment content of zygotes was 82% lower than vegetative cells, even though they appeared darker under the microscope. Zygotes of S. lachrymosa contained significantly higher cellular concentrations of β‐carotene (0.65 ± 0.15 pg · cell−1) than all other life stages. Photoprotective pigments and the de‐epoxidation ratio of xanthophylls‐cycle pigments in S. lachrymosa were significantly elevated in zygotes and cysts compared to other stages. This suggests a role for accessory pigments in combating intracellular oxidative stress during sexual reproduction or encystment. Resting cysts contained some pigments even though chloroplasts were not visible, suggesting that the brightly colored accumulation body contained photosynthetic pigments. The differences in pigmentation between life stages have implications for interpretation of pigment data from field samples when sampled during dinoflagellate blooms.

CONSUMPTION OF SCRIPPSIELLA LACHRYMOSA RESTING CYSTS BY THE EASTERN OYSTER (CRASSOSTREA VIRGINICA)

ABSTRACT Scrippsiella spp. resting cysts, unlike many other dinoflagellate cysts, possess an outer layer of calcite beneath which is a thin sporopollenin wall. This feature may affect cyst survival through the digestive tract of benthic organisms, when they consume the cysts. The extent of digestibility is related to the degree to which grazing by benthic organisms could influence a benthic cyst population. To test consumption and digestion of a representative Scrippsiella cyst by one benthic grazer, the eastern oyster (Crassostrea virginica) was fed culture-produced resting cysts of the dinoflagellate Scrippsiella lachrymosa under controlled conditions. Cyst recovery from no-oyster, control containers was 97%; therefore, digestive destruction of cysts could be quantified as the difference between cysts added to experimental containers containing oysters and the number of intact cysts recovered after a period of oyster feeding. In each treatment, 18% of the cysts were destroyed after being ingested at a cell density of 43.4 cysts/mL and 11% were digested at a higher cell density (263.2 cysts/mL). Cysts were observed to become rounded and turn yellow after first losing the outer, calcareous wall as a first step in digestion. In fecal-pellet samples, contents from broken cysts could be found as well as intact cysts and rounded yellow cysts. Viability of ingested cysts was not evaluated, but it seems that Scrippsiella cysts are relatively resistant to digestion by oysters.