Bengt Karlson

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.

Diversity of Pico- to Mesoplankton along the 2000 km Salinity Gradient of the Baltic Sea

Microbial plankton form the productive base of both marine and freshwater ecosystems and are key drivers of global biogeochemical cycles of carbon and nutrients. Plankton diversity is immense with representations from all major phyla within the three domains of life. So far, plankton monitoring has mainly been based on microscopic identification, which has limited sensitivity and reproducibility, not least because of the numerical majority of plankton being unidentifiable under the light microscope. High-throughput sequencing of taxonomic marker genes offers a means to identify taxa inaccessible by traditional methods; thus, recent studies have unveiled an extensive previously unknown diversity of plankton. Here, we conducted ultra-deep Illumina sequencing (average 105 sequences/sample) of rRNA gene amplicons of surface water eukaryotic and bacterial plankton communities sampled in summer along a 2000 km transect following the salinity gradient of the Baltic Sea. Community composition was strongly correlated with salinity for both bacterial and eukaryotic plankton assemblages, highlighting the importance of salinity for structuring the biodiversity within this ecosystem. In contrast, no clear trends in alpha-diversity for bacterial or eukaryotic communities could be detected along the transect. The distribution of major planktonic taxa followed expected patterns as observed in monitoring programs, but groups novel to the Baltic Sea were also identified, such as relatives to the coccolithophore Emiliana huxleyi detected in the northern Baltic Sea. This study provides the first ultra-deep sequencing-based survey on eukaryotic and bacterial plankton biogeography in the Baltic Sea.

The Copernicus Marine Environment Monitoring Service Ocean State Report

ABSTRACT The Copernicus Marine Environment Monitoring Service (CMEMS) Ocean State Report (OSR) provides an annual report of the state of the global ocean and European regional seas for policy and decision-makers with the additional aim of increasing general public awareness about the status of, and changes in, the marine environment. The CMEMS OSR draws on expert analysis and provides a 3-D view (through reanalysis systems), a view from above (through remote-sensing data) and a direct view of the interior (through in situ measurements) of the global ocean and the European regional seas. The report is based on the unique CMEMS monitoring capabilities of the blue (hydrography, currents), white (sea ice) and green (e.g. Chlorophyll) marine environment. This first issue of the CMEMS OSR provides guidance on Essential Variables, large-scale changes and specific events related to the physical ocean state over the period 1993–2015. Principal findings of this first CMEMS OSR show a significant increase in global and regional sea levels, thermosteric expansion, ocean heat content, sea surface temperature and Antarctic sea ice extent and conversely a decrease in Arctic sea ice extent during the 1993–2015 period. During the year 2015 exceptionally strong large-scale changes were monitored such as, for example, a strong El Niño Southern Oscillation, a high frequency of extreme storms and sea level events in specific regions in addition to areas of high sea level and harmful algae blooms. At the same time, some areas in the Arctic Ocean experienced exceptionally low sea ice extent and temperatures below average were observed in the North Atlantic Ocean.

Harmful Algal Blooms in a Changing Ocean

Climate change research has progressed rapidly over the last two decades, with model projections of future climate conditions gaining enough consensus to enable downscaling these changes to regional scales. While the field of HAB research has come far since its early roots, our current understanding is not well suited to utilize advances in climate modeling to project how HABs’ prevalence and character may differ in the future oceans. This situation largely is due to the complexity of interspecies competition, but it also can be attributed to the “insular” nature of HAB research. HAB studies focus more on the HAB organism, often in isolated cultures, than on the phytoplankton community in which it may or may not flourish. Even though GEOHAB fostered comparative research, it most often is not possible to quantitatively compare among published HAB studies because nonuniform methods are used. Most HAB observational programs are triggered only when toxic species abundances become high enough to threaten human health, so the specific conditions that catalyze these bloom developments cannot be described. It is difficult then to project how changing environmental conditions may influence the development of HABs, particularly given that these events generally are comparatively rare within the context of dynamic coastal ecosystems. Participants in an international workshop considered these issues and identified a number of specific steps, presented in small part here, that will help HAB research to obtain compelling evidence that climate change is impacting HAB distribution, prevalence, or character. New HAB research strategies are needed if we are to develop informed projections for HABs under anticipated end-of-century conditions in the future oceans.

A potential tool for high-resolution monitoring of ocean acidification

Current anthropogenic carbon dioxide emissions generate besides global warming unprecedented acidification rates of the oceans. Recent evidence indicates the possibility that ocean acidification and low oceanic pH may be a major reason for several mass extinctions in the past. However, a major bottleneck for research on ocean acidification is long-term monitoring and the collection of consistent high-resolution pH measurements. This study presents a low-power (<1 W) small sample volume (25 μL) semiconductor based fluorescence method for real-time ship-board pH measurements at high temporal and spatial resolution (approximately 15 s and 100 m between samples). A 405 nm light emitting diode and the blue and green channels from a digital camera was used for swift detection of fluorescence from the pH sensitive dye 6,8-Dihydroxypyrene-1,3-disulfonic acid in real-time. Main principles were demonstrated by automated continuous measurements of pH in the surface water across the Baltic Sea and the Kattegat region with a large range in salinity (~3-30) and temperature (~0-25°C). Ship-board precision of salinity and temperature adjusted pH measurements were estimated as low as 0.0001 pH units.

Allochthonous matter: an important factor shaping the phytoplankton community in the Baltic Sea

It is well-known that nutrients shape phytoplankton communities in marine systems, but in coastal waters allochthonous dissolved organic matter (ADOM) may also be of central importance. We studied how humic substances (proxy of ADOM) and other variables influenced the nutritional strategies, size structure and pigment content of the phytoplankton community along a south–north gradient in the Baltic Sea. During the summer, the proportion of mixotrophs increased gradually from the phosphorus-rich south to the ADOM-rich north, probably due to ADOM-fueled microbes. The opposite trend was observed for autotrophs. The chlorophyll a (Chl a): carbon (C) ratio increased while the levels of photoprotective pigments decreased from south to north, indicating adaptation to the darker humic-rich water in the north. Picocyanobacteria dominated in phosphorus-rich areas while nanoplankton increased in ADOM-rich areas. During the winter–spring the phytoplankton biomass and concentrations of photoprotective pigments were low, and no trends with respect to autotrophs and mixotrophs were observed. Microplankton was the dominant size group in the entire study area. We conclude that changes in the size structure of the phytoplankton community, the Chl a:C ratio and the concentrations of photoprotective pigments are indicative of changes in ADOM, a factor of particular importance in a changing climate.

GlobalHAB: Fostering International Coordination on Harmful Algal Bloom Research in Aquatic Systems

GlobalHAB, “Global Harmful Algal Blooms,” is a new scientific programme on harmful algal blooms (HABs) cosponsored by the Intergovernmental Oceanographic Commission (IOC) of UNESCO and the Scientific Committee on Oceanic Research (SCOR) that will operate for 10 years from 2016 to 2025. GlobalHAB builds on the solid foundation established by the former programme GEOHAB and will continue to promote coordinated international scientific activities, which is fundamental to keep progressing on the comprehension of the global complexity of HABs and that will contribute to the management and mitigation of their impacts worldwide. The GlobalHAB Scientific and Implementation Plan is briefly presented in this chapter.

Determination of phytoplankton abundances (Chlorophyll-a) in the optically complex inland water - The Baltic Sea

A novel approach, termed Summed Positive Peaks (SPP), is proposed for determining phytoplankton abundances (Chlorophyll-a or Chl-a) and surface phytoplankton bloom extent in the optically complex Baltic Sea. The SPP approach is established on the basis of a baseline subtraction method using Rayleigh corrected top-of-atmosphere data from the Medium Resolution Imaging Spectrometer (MERIS) measurements. It calculates the reflectance differences between phytoplankton related signals observed in the MERIS red and near infrared (NIR) bands, such as sun-induced chlorophyll fluorescence (SICF) and the backscattering at 709nm, and considers the summation of the positive line heights for estimating Chl-a concentrations. The SPP algorithm is calibrated against near coincident in situ data collected from three types of phytoplankton dominant waters encountered in the Baltic Sea during 2010 (N=379). The validation results show that the algorithm is capable of retrieving Chl-a concentrations ranging from 0.5 to 3mgm-3, with an RMSE of 0.24mgm-3 (R2=0.69, N=264). Additionally, the comparison results with several Chl-a algorithms demonstrates the robustness of the SPP approach and its sensitivity to low to medium biomass waters. Based on the red and NIR reflectance features, a flagging method is also proposed to distinguish intensive surface phytoplankton blooms from the background water.