Mikko Kiirikki

Life Strategies of Filamentous Algae in the Northern Baltic Proper

Abstract Short lived filamentous algae are a major component of the rocky-shore macroalgal vegetation of eutrophic waters in the Baltic Sea. They show considerable variation in abundance both seasonally and from year to year. In this study the seasonal pattern of growth and reproduction is documented in six species to outline their life strategies. Five of the species studied were reproductive in summer or autumn, just after a period of active growth. Pilayella littoralis was the only exception. It grew fast in the spring but reproduction was successful only in winter, when only the basal parts of plants were left. The amount of filamentous algae was very low in winter. The only species which survived the winter period as macroscopic filaments was Ceramium tenuicorne. At least three species, Cladophora glomerata, Dictyosiphonfoeniculaceus and Ectocarpus siliculosus, relied on microscopic stages to survive the unfavourable winter period. Responses of these filamentous species to variations in their physica...

Searching efficient protection strategies for the eutrophied Gulf of Finland: the combined use of 1D and 3D modeling in assessing long-term state scenarios with high spatial resolution

Abstract An experiment combining the use of two ecosystem models was conducted to search for effective protection strategies for the Gulf of Finland (Baltic Sea). Reference and scenario simulations were first run with a one-dimensional (1D) model for seven main basins of the entire Baltic Sea until steady state was achieved. The obtained basinwise distributions of inorganic nitrogen (N) and phosphorus (P), as well as sediment labile P, were then used to initiate 5-y simulations with a three-dimensional (3D) ecosystem model. The results suggest that relatively small local load reductions (the “Finland” scenario) would improve only the state of adjacent coastal waters significantly. This would be the case, even for runs covering several decades, which clearly exceed the residence times of nutrients in the Gulf of Finland. A significant decrease from a substantial loading source to the Gulf (the “St. Petersburg” scenario) would decrease cyanobacterial biomasses in the entire Gulf of Finland and also immediately outside it. A reduction in the current Polish nutrient loads would improve the situation in the whole Baltic Proper and cause an extensive decline in cyanobacterial biomasses in the Gulf of Finland, as well. However, it would take several decades until the improvement caused by reducing loads in the “Poland” scenario is seen, while in the “St. Petersburg” scenario the corresponding time lag would only be a few years. Our results suggest that the common water protection policy in the Baltic Sea region should have the largest nutrient sources as its primary target, regardless of their location and country.

Integrating Ecological and Economic Modeling of Eutrophication: Toward Optimal Solutions for a Coastal Area Suffering from Sediment Release of Phosphorus

Abstract This paper puts forward a model for managing eutrophication that integrates the salient ecological and economic characteristics of a coastal area suffering from severe nutrient enrichment. The model links the development of phosphorus concentration over time to nutrient emissions from agriculture and habitation. It accounts for differences in agricultural and municipal abatement options and their costs, as well as the need to undertake irreversible investments to set up wastewater treatment facilities. Furthermore, it considers sediment release of phosphorus as a function of annual nutrient loads. The model is parameterized for a 30-km-wide area off the Finnish coast of the Gulf of Finland. The socially optimal policy, which minimizes the sum of monetary damage caused by eutrophication and the costs of nutrient abatement over time, is determined using a dynamic programming approach. The results suggest that considerable investments are warranted to bring wastewater treatment facilities up to date. Continued efforts to reduce agricultural nutrient loading are nevertheless also called for. The analysis provided is a first step toward an integrated analysis of eutrophication that accounts for complexities inherent in the problem, such as sediment release of phosphorus and irreversible investments in abatement technology. The results are sensitive in particular to ecological assumptions and parameterization, and further research is needed in these areas.

Linking the growth of filamentous algae to the 3D-ecohydrodynamic model of the Gulf of Finland

Abstract One of the most visible symptoms of eutrophication in the Gulf of Finland is blooms of unattached filamentous algae. This decomposing algal biomass causes serious nuisance problems for recreational uses of the coastal zone, particularly when cast ashore. The nutrient availability for these macroscopic filamentous algae is regulated by a superior competitor, the phytoplankton. Nutrients are left for the weaker competitor only when the conditions are not suitable for the growth of phytoplankton. This happens during vertical mixing of the water column. The lack of stratification prevents the formation of phytoplankton blooms, but does not limit the growth of filamentous algae when still growing attached to the bottom. A simple growth model was developed to describe the growth and biomass of filamentous algae. In the absence of suitable nutrient measurements, the model was linked to a 3D-ecohydrodynamic model which generated the nutrient input data. The model was calibrated with three-year monitoring data of filamentous algal biomass at one location. Validation was carried out with one-year monitoring data from an adjacent location. The model was able to describe the number of biomass peaks and their timing with good accuracy. After further development, the filamentous algal model will be used as one of the management tools for the evaluation of the sustainable nutrient load to the Gulf of Finland.

Sunlight, shade and tidal night: Photoadaptation in Fucus vesiculosus L.

Abstract This investigation compares two populations of Fucus vesiculosus L. in which the lower bathymetric limits are determined by insufficient light rather than by the presence of a superior algal competitor. In the tidal reaches of the R. Mersey (NW England), water turbidity is so severe that Fucus experiences darkness when covered by an incoming tide. These plants must therefore photosynthesise only when emergent and are hence exposed to full sunlight. Baltic Sea (SW Finland) Fucus, in contrast, is permanently submerged in an atidal environment and subject to shade conditions that increase with depth. Chlorophyll concentrations and ratios in these populations differ significantly. Significant morphological differences are also present, with Baltic thalli showing distal blade expansion and Mersey thalli proximal expansion. A transplant experiment involving Baltic thalli from different sites and depths suggested that morphological plasticity had a minor role in the observed differences. The adaptive im...

3D Ecosystem Models as Decision Support Tools in the Gulf of Finland — the Kotka Archipelago as an Example

The Gulf of Finland is one of the most eutrophied areas of the Baltic Sea. The major part of the nutrient load enters the sea outside Finnish borders from the metropolis of St. Petersburg and the river Neva. Finnish local authorities are facing a difficult task of defining water protection measures, when the effects of local measures have to be weighted against transboundary influences. This complex situation can be demonstrated visually with the help of mathematical modelling.