Lena Kautsky

Integrated marine cultivation of Gracilaria chilensis (Gracilariales, Rhodophyta) and salmon cages for reduced environmental impact and increased economic output

Integrated marine cultivation of Gracilaria chilensis (Gracilariales, Rhodophyta) and salmon cages for reduced environmental impact and increased economic output

Hydroxylated and methoxylated polybrominated diphenyl ethers and polybrominated dibenzo-p-dioxins in red alga and cyanobacteria living in the Baltic Sea.

Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs) are present in the ecosystem of the Baltic Sea. OH-PBDEs are known to be both natural products from marine environments and metabolites of the anthropogenic polybrominated diphenyl ethers (PBDEs), whereas, MeO-PBDEs appear to be solely natural in origin. Polybrominated dibenzo-p-dioxins (PBDDs) are by-products formed in connection with the combustion of brominated flame retardants (BFRs), but are also indicated as natural products in a red alga (Ceramium tenuicorne) and blue mussels living in the Baltic Sea. The aims of the present investigation were to quantify the OH-PBDEs and MeO-PBDEs present in C. tenuicorne; to verify the identities of PBDDs detected previously in this species of red alga and to investigate whether cyanobacteria living in this same region of the Baltic Sea contain OH-PBDEs, MeO-PBDEs and/or PBDDs. The red alga was confirmed to contain tribromodibenzo-p-dioxins (triBDDs), by accurate mass determination and additional PBDD congeners were also detected in this sample. This is the first time that PBDDs have been identified in a red alga. The SigmaOH-PBDEs and SigmaMeO-PBDEs concentrations, present in C. tenuicorne were 150 and 4.6 ng g(-1) dry weight, respectively. In the cyanobacteria 6 OH-PBDEs, 6 MeO-PBDEs and 4 PBDDs were detected by mass spectrometry (electron capture negative ionization (ECNI)). The PBDDs and OH-PBDEs and MeO-PBDEs detected in the red alga and cyanobacteria are most likely of natural origin.

Integrated tank cultivation of salmonids and Gracilaria chilensis (Gracilariales, Rhodophyta)

Oncorhynchus kisutch, O. mykiss and Gracilaria chilensis cultivation in intensive tank systems is feasible. The environmental benefits associated with the development of integrated tank cultivation were established by analyzing previously published and unpublished data on fish production and food conversion efficiency, particle discharges in fish effluents, as well as biomass production, nutrient uptake efficiency data of Gracilaria, with special emphasis on ammonium. The results indicate that fish production can reach 30 kg m−3 during a production cycle, and food conversion can be maintained stably at 1.4 g food g fish−1 production during the entire cultivation period. The solid particle discharges can be as high as 2.1 g (dry) kg fish−1 day−1 during the spring and summer, when salmon cultivation reaches its highest densities. The nutrient that increases most in fish effluents is ammonium, reaching concentrations as high as 500 µg 1−1, also in spring and summer. Gracilaria production can reach production rates as high as 48.9 kg m−2 year−1 and is able to remove 50% of the dissolved ammonium in winter, increasing to 90–95% in spring. These results are integrated into an income-analysis model, adding the extra income for Gracilaria harvesting and internalizing the environmental benefits for a 100-ton salmon production unit, which indicates that an additional total revenue of over US

Distributional success of the marine seaweedFucus vesiculosus L. in the brackish Baltic Sea correlates with osmotic capabilities of Baltic gametes

60 000, representing around 10% of the total income, is possible.

Intriguing asexual life in marginal populations of the brown seaweed Fucus vesiculosus

To understand the unique success of the marine seaweedFucus vesiculosus L. (PHaeophyceae) in the brackish Baltic Sea, the performance of gametes from Baltic [4.1–6.5‰S (Salinity)] and marine populations was studied. Sperm from BalticF. vesiculosus swam with a path velocity of c. 30–110 μm/s and could fertilize eggs in waters of salinities from 4 to 33‰S. In their natural water, Baltic sperm were not negatively phototactic, unlike marine sperm in seawater; this should decrease the sperm:egg concentration at the seafloor and reduce the likelihood of polyspermy. Marine (Iceland, Sweden) sperm in seawater had a path velocity of c. 80–100 μm/s, but performed poorly and could not fertilize eggs in natural or artificial Baltic water ≤6‰S; therefore, Baltic populations have adapted or acclimated to their brackish habitat. Baltic populations appear better adapted to their natural low salinities because, even after culturing Baltic and marine individuals in water from both the Baltic (6.5‰S) and the marine Skagerrak (21‰S), Baltic sperm were in both cases still able to swim and fertilize eggs at lower salinities (4‰S) than marine sperm; fertilization never occurred between marine gametes at 4–6‰S. However,F. vesiculosus acclimates to some salinities, since sperm from Baltic and marine males that had been cultured at 21‰S swam better (higher velocity, proportion that were motile and/or linearity) in marine salinities (21–33‰S) than when they were cultured at 6.5‰S. The effects of salinity on sperm motility and fertilization were osmolar rather than due to specific ionic requirements, over the tested range. The osmolalities (< c. 100 mmol/kg) at which fertilization success of Baltic gametes decreases nearly to zero correspond to the osmolality of Baltic water at the northernmost limit of distribution ofF. vesiculosus in the Baltic Sea. Therefore, the present range ofF. vesiculosus in the Baltic appears to correspond to the osmotic tolerance of the gametes. Very small natural or anthropogenic increases in ambient osmolality would be likely to cause a substantial expansion of this species into the inner Baltic.

GENETIC AND MORPHOLOGICAL IDENTIFICATION OF FUCUS RADICANS SP. NOV. (FUCALES, PHAEOPHYCEAE) IN THE BRACKISH BALTIC SEA1

Reproduction of attached large brown algae is known to occur only by sexual zygotes. Using microsatellites we show evolution of asexual reproduction in the bladder wrack promoting population persistence in the brackish water Baltic Sea (< 6 psu). Here a dwarf morph of Fucus vesiculosus is dominated by a single clone but clonal reproduction is also present in the common form of the species. We describe a possible mechanism for vegetative reproduction of attached algae, and conclude that clonality plays an important role in persistence and dispersal of these marginal populations, in which sexual reproduction is impaired by low salinity.

REPRODUCTIVE SUCCESS OF FUCUS VESICULOSUS (PHAEOPHYCEAE) IN THE BALTIC SEA

Brown seaweeds of the genus Fucus occupy a wide variety of temperate coastal habitats. The genus is evolutionary dynamic with recent radiations to form morphologically distinct taxa. In the brackish Baltic Sea, fucoids are the only perennial canopy‐forming macroalgae. The most northern populations of Fucus occur permanently submerged in extremely low salinity (3–5 psu). These are currently referred to as Fucus vesiculosus L. but are morphologically distinct with a narrow frond without bladders. We report here that a population of this unique morphotype is reproductively isolated from a truly sympatric population of common F. vesiculosus and conclude that the northern morphotype represents a previously undescribed species. We describe Fucus radicans sp. nov., which is attached and dioecious with broadly elliptic receptacles, characterized by a richly branched narrow flat frond (2–5 mm), short thallus (<26 cm), and a high capacity for vegetative recruitment of attached plants. Analysis of five highly polymorphic microsatellite DNA loci showed genetic differentiation between sympatric populations of F. radicans and F. vesiculosus, whereas allopatric populations of the same species revealed a coherent pattern of genetic variation. Sequences of the RUBISCO region in F. radicans were identical to or differing at only one to two dinucleotide positions from those of F. vesiculosus, indicating a recent common origin of the two species.

Rapid speciation in a newly opened postglacial marine environment, the Baltic Sea.

Marine organisms colonizing brackish habitats such as the Baltic Sea must cope with the negative effects of low salinities on reproductive success because these may reduce gamete viability and/or increase polyspermy. Reproductive characteristics of the marine seaweed Fucus vesiculosus L. were studied in several brackish habitats, particularly in the northern Baltic Sea, to understand its ability to reproduce where few other marine species survive. Polyspermy and fertilization success were variable at the boundary of the continuous distribution of F. vesiculosus in the Baltic Sea, and polyspermy was high (10%–30%) when fertilization was successful. A strong female bias (80%–86%, ca. 5.5:1) was found at the northernmost limit of Baltic F. vesiculosus. Electrophysiological studies showed that many eggs have a high input resistance (519 ± 150 MΩ[mean ± SE, n = 14] at Drivan, 1995), which may be helpful in preventing polyspermy in this brackish habitat. The polyspermy block remains sodium‐dependent in the northern Baltic. Sperm bound quickly to northern Baltic eggs in natural water, but fertilization was delayed compared to marine F. vesiculosus. A subset of northern Baltic eggs studied during an optimal reproductive period (7–11 July 1995) had a membrane potential (Em) of ca. −100 mV and an effective fertilization potential (FP) of ca. 2 min with a plateau of −25 mV, but repolarized too rapidly for the FP to be protective. Pronuclear migration and cell wall secretion occurred more slowly in Baltic than in marine zygotes. The reproductive success of theseboundary populations may be dependent upon windows of opportunity when there are favorable combinations of the levels of salinity, water motion, population density, and sex ratio. These factors and the short duration of the reproductive season in the northern Baltic Sea may result in reproductive failure in some years.

Effects of filamentous algae and deposited matter on the survival of Fucus vesiculosus L. germlings in the Baltic Sea

BackgroundTheory predicts that speciation can be quite rapid. Previous examples comprise a wide range of organisms such as sockeye salmon, polyploid hybrid plants, fruit flies and cichlid fishes. However, few studies have shown natural examples of rapid evolution giving rise to new species in marine environments.ResultsUsing microsatellite markers, we show the evolution of a new species of brown macroalga (Fucus radicans) in the Baltic Sea in the last 400 years, well after the formation of this brackish water body ~8–10 thousand years ago. Sympatric individuals of F. radicans and F. vesiculosus (bladder wrack) show significant reproductive isolation. Fucus radicans, which is endemic to the Baltic, is most closely related to Baltic Sea F. vesiculosus among north Atlantic populations, supporting the hypothesis of a recent divergence. Fucus radicans exhibits considerable clonal reproduction, probably induced by the extreme conditions of the Baltic. This reproductive mode is likely to have facilitated the rapid foundation of the new taxon.ConclusionThis study represents an unparalleled example of rapid speciation in a species-poor open marine ecosystem and highlights the importance of increasing our understanding on the role of these habitats in species formation. This observation also challenges presumptions that rapid speciation takes place only in hybrid plants or in relatively confined geographical places such as postglacial or crater lakes, oceanic islands or rivers.

Increased chemical resistance explains low herbivore colonization of introduced seaweed

As a result of increased nutrient levels in the Baltic Sea during thepast 50 years, mass developments of filamentous algae have become a commonfeature along the Swedish east coast and deposition of organic matter has alsoincreased. To test whether these two factors have any effects on the early lifestages of Fucus vesiculosus a number of laboratory andfield studies were conducted. The amount of epilithic and epiphytic filamentousalgae on F. vesiculosus and the amount of deposited matterin the littoral zone were quantified during the two reproductive periods ofF. vesiculosus, early summer (May–June) and lateautumn (September–October). Both filamentous algae (Cladophoraglomerata) and deposited matter (introduced either before or aftersettlement of fertilized eggs) were shown to significantly decrease the numberof surviving germlings. The survival of germlings seeded on stones withfilamentous algae, or seeded on culture dishes concurrently with the lowestconcentration of deposited matter (0.1 g dm−2),was 5% or less. In the field, the amount of filamentous algae was significantlyhigher during F. vesiculosus summer reproduction, whereasthe amount of deposited matter collected in traps was significantly higherduring the period of autumn reproduction. The greatest biomass of filamentousalgae was observed at sheltered sites. Based on the negative effects offilamentous algae and deposited matter on Fucusrecruitmentand the observation of local and seasonal differences in abundance offilamentous algae and deposition, we suggest that the prerequisites for thesurvival of either summer or autumn-reproducing populations of F.vesiculosus in the Baltic Sea may differ locally.