Ecotypic differentiation in light-related traits of the kelp Laminaria saccharina

Light-related traits were compared for Laminaria saccharina Lamour. collected from three habitats in Maine and New York, USA, with different ambient light regimes. Light-level, expressed as a proportion of surface irradiance (I₀), ranged from 0.04 to 0.32 I₀ in the shallow habitat, but rarely exceeded 0.04 I₀ in the deep and turbid habitats. Juvenile sporophytes collected from each habitat in April, 1985, were grown at four acclimation light-levels (0.065, 0.12, 0.26, and 0.54 I₀) in a common-garden, laboratory experiment. Photosynthesis vs irradiance (PI) parameters, light-harvesting characteristics, and rates of carbon-assimilation and growth were determined for each group of plants. The results indicated that ecotypic differentiation had occurred among the three kelp populations. Photosynthetic capacity (P_max) and photosynthetic efficiency () were generally highest for plants from the turbid habitat, lowest for deep plants, and intermediate for shallow plants. These differences were largely attributable to variations in light-harvesting characteristics. The nature and magnitude of photoacclimation responses also differed among populations. Population differences in photosynthetic parameters resulted in different rates of C-assimilation and growth by plants from shallow, deep, and turbid habitats. Predictions of in situ growth rates indicated that the severity of light-limitation and, therefore, the adaptive significance of efficient light-utilization vary among the three populations. It is concluded that ecotypic differentiation in light-related traits is important to the broad environmetal range of L. saccharina.     

Ecotypic differentiation in the marine diatom Skeletonema costatum: influence of light intensity on the photosynthetic apparatus

Three genetically distinct clones of Skeletonema costatum (Grev.) Cleve were grown at 20°C under high (274 E m^-2 s^-1) and low (27 E m^-2 s^-1) light conditions and their photoadaptive photosynthetic responses compared. When all three clones were grown under low light, pigment analyses and fluorescence excitation spectra demonstrated that the accessory pigments, chlorophyll c and fucoxanthin, became more important in light-harvesting compared to chlorophyll a. Photosynthetic unit sizes increased for Photosystems I and II in low light, but photosynthesis vs irradiance characteristics were not reliable predictors of photosynthetic unit features. Fluorescence excitation spectra and photosynthesis vs irradiance (P-I) relationships indicated that changes in energy transfer occurred independent of changes in pigment content. Large increases in accessory pigment content were not accompanied by large increases in excitation from these pigments. Changes in energy transfer properties were as important as changes in PSU size in governing the photoadaptive responses of S. costatum. When the three clones were grown under identical conditions, each had a separate and distinct pattern of photoadaptation. Significant differences among clones were found for pigment ratios, photosynthetic unit sizes for Photosystems I and II and efficiency of energy transfer between pigments. These strikingly different photoadaptive strategies among clones may partially account for the great ecological success of the diatom species. This is the first quantitative investigation of the importance of both chlorophyll c and fucoxanthin to the adaptive responses of diatoms to light intensity, and represents the most complete characterization of the photoadaptive responses of a single species of marine phytoplankter to differences in light environment.     

Ecotypic differentiation of Laminaria longicruris in relation to seawater nitrate concentration

The ultraplankton (cell diameters >3 μm), which compromises about 70% of the biomass of phytoplankton in subtropical surface waters near Oahu, Hawaii, was isolated for growth rate studies. The specific growth rate (μ) was estimated from the rate of increase of the chlorophyll biomass during incubations in the absence of grazers. This growth rate of the ultraplankton ranged from 0.037 to 0.071 h^?1 (=1.3 to 2.5 doublings d^?1) during a period when P:B ratios of 5 to 14.5 μg C μg^?1 chl a h^?1 prevailed. The co-occurrence of atypically high P:B ratios and nonlimiting ambient nutrient concentrations suggests that the calculated values are higher than those characteristic of such subtropical ecosystems in general. Rates of ammonium uptake and photosynthesis by the >3 μm fraction were also compared to those of larger fractions. Organisms in the >3 μm fraction assimilated NH ₄ ⁺ at a rate which was about 75% greater than that of the 3 to 20 μm size fraction. Comparison of μ and P:B data collected over a 2 mo period (November–December, 1980) shows that the correlation between these two rate indices is nonlinear. The predominance of small-celled phytoplankton in oligotrophic waters is explained, in part, by its higher μ, its higher nutrient assimilation rates, and the absence of its loss through sedimentation.     

Positive buoyancy in eel leptocephali: an adaptation for life in the ocean surface layer

Many planktonic organisms have adaptations such as floats or lighter substances to obtain buoyancy to help them remain in the surface layer of the ocean where photosynthetic primary production occurs and food is most abundant. The almost totally transparent eel larvae, called leptocephali, are a unique member of the planktonic community of the surface layer, but their ecology and physiology are poorly understood. We conducted a comparative study on the specific gravity of planktonic animals including 25 taxa of 7 phyla of marine invertebrates and 6 taxa of leptocephali (vertebrate) to gain a broad perspective on the buoyancy of the eggs and larval stages of the Japanese eel. The specific gravity values of the various freshly caught marine invertebrate taxa varied widely from 1.020 to 1.425, but leptocephali had some of the lowest values (1.028–1.043). Artificially cultured live leptocephali had even greater buoyancies with specific gravities of 1.019–1.025 that were close to or lower than seawater, and their buoyancy showed ontogenetic changes among the different early life history stages. Leptocephali appear to have a unique mechanism of buoyancy control by chloride cells all over body surface through osmoregulation of body fluid contained in the extracellular matrix of transparent gelatinous glycosaminoglycans filling their bodies. This adaptation is likely a key factor for their survival by helping them to remain in the surface layer where food particles are the most abundant, while being transparent for predator avoidance. The ontogenetic change in buoyancy of eel eggs, leptocephali and glass eels likely enhances their larval survival, transport, and recruitment to terrestrial freshwater habitats.     

Temperature acclimation of respiration and photosynthesis in the brown algaLaminaria saccharina

Sporophytes of the brown algaLaminaria saccharina (L.) Lamour grown at 15°C contained significantly more chlorophylla (chla) than did similar plants grown at 5°C. The increase in chla in 15°C plants was due to increased numbers of photosystem II reaction centes, and possibly to increased photosynthetic unit size, compared with 5°C plants. These changes were associated with increased values (photosynthetic efficiencies) in 15°C-grownL. saccharina relative to 5°C-grown plants. The changes in together with reduced respiration rates allowed 15°C-grownL. saccharina to achieve net photosynthesis and light-saturated photosynthesis at a lower photon fluence rate (PFR) than 5°C plants when both groups were assayed at the same temperature (15°C). The photon fluence rates necessary to reach the compensation point and achieve light-saturated photosynthesis (I _c andI _k , respectively) increased with increasing incubation temperature inL. saccharina grown at both 5 and 15°C. However, acclimation responses to growth temperature compensated for the short-term effect of temperature onI _c andI _k . Consequently, plants grown at 5 and 15°C were able to achieve similar rates of light-limited photosynthesis, and similarI _c andI _k values at their respective growth temperatures. These responses are undoubtedly important for perennial seaweeds such asL. saccharina, which frequently grow in light-limited habitats and experience pronounced seasonal changes in water temperature.Please address all correspondence and requests for reprints to I.R. Davison     

The life cycle ofClytia attenuata (calyptoblastea: Campanulariidae)

The life cycle of the hydroidClytia attenuata (Calkins) (Calyptoblastea: Campanulariidae) has been completed in the laboratory including development of the medusa, previously described asPhialidium lomae Torrey (Leptomedusae: Campanulariidae). Under laboratory conditions, the hydroid exhibits some morphological variation. Characteristic branching of the hydroid occurs at temperatures between 17° to 19°C. At 13° to 15°C the colonies are unbranched and cannot be distinguished fromClytia cylindrica L. Agassiz. Young medusae are similar to other young species ofPhialidium. Development to the adult form requires 25 to 30 days at 17° to 24°C. The adult medusae are 6 to 10 mm in diameter, watch-glass shaped, and have 20 to 28 tentacles. Based on the adult medusa,Clytia attenuata is maintained as a valid species.     

Carbon emission analysis of a residential building in China through life cycle assessment

In this paper, a quantitative life cycle model for carbon emission accounting was developed based on the life cycle assessment (LCA) theory. A residential building in Sino-Singapore Tianjin Eco-city (Tianjin, China) was selected as a sample, which had been constructed according to the concept of green environmental protection and sustainable development. In the scenario of this research, material production, construction, use and maintenance, and demolition phases were assessed by building carbon emission models. Results show that use and maintenance phase and material production phase are the most significant contributors to the life cycle carbon emissions of a building. We also analyzed some factor influences in LCA, including the thickness of the insulating layer and the length of building service life. The analysis suggest that thicker insulating layer does not necessarily produce less carbon emissions in the light of LCA, and if service life of a building increases, its carbon emissions during the whole life cycle will rise as well but its unit carbon emission will decrease inversely. Some advices on controlling carbon emissions from buildings are also provided.     

“Free space-photosynthesis” in the algae Fucus virsoides and Laminaria saccharina

This paper deals with the role of bicarbonates in the apparent free space (AFS) and their importance for the photosynthetic process. Both the littoral alga Fucus virsoides (Mediterranean Sea) and the sublittoral alga Laminaria saccharina (Baltic Sea) show the same response. Unloading of Clions and subsequent reloading of HCO₃-ions result in a positive photosynthetic rate in distilled water (free of CO₂). Time of exposure of an algal thallus to bicarbonate solutions, as well as the concentration of these solutions, influences AFS-assimilation of the ions.     

生命周期评价在我国的应用

生命周期评价(LCA)是一种有效的清洁生产诊断和评价工具,其理念已经逐步引入我国,并在诸多领域得到不同程度的应用.根据清洁生产的要求,LCA有望在清洁生产审核、产品生态设计、废物管理、生态工业等方面发挥更大的作用.目前应尽快引进和消化吸收国际上先进的LCA方法,建立符合中国国情的LCA方法学体系和数据支撑体系,并在此基础上开展各个领域、各种形式的应用研究与示范.     

Clustering economic sectors in China on a life cycle basis to achieve environmental sustainability

To improve material efficiency, industrial structure optimization becomes a focal point in Chinese industrial and environmental policies. It is crucial to cluster economic sectors and determine their priority for industrial and environmental policy implementation. Integrating a set of criteria, a hybrid input-output model and the hierarchical cluster analysis, this study clusters China’s economic sectors and determines their priority on a life cycle basis. China’s economic sectors are clustered into three clusters. Industrial structure changes (industrial policy) should encourage the development of sectors in cluster 1 and limit the development of sectors in cluster 2. Technology development and materials recycling (two environmental policies) should mainly focus on sectors in clusters 1 and 2. Future industrial policies in China should limit the development of two sectors named Manufacture of metal products and Extraction of petroleum and natural gas. Instead of limiting some industries by command-and-control, the best policy option is to remedy environmental standards and law enforcement. Enterprises belonging to the identified key sectors from the viewpoint of direct production impacts should be concerned to achieve enterprise sustainability. To achieve sustainable production chains, the identified key sectors from the viewpoint of accumulative production impacts should be concerned. For sustainable consumption, the identified key sectors from the viewpoint of consumption impacts should be concerned to transform consumption styles. Most of environmental pressure can be alleviated not only by technical improvements and material recycling, but also by the development of economic sectors in cluster 1.     

In-situ studies on the life cycle of Diastylis rathkei (Cumacea: Crustacea)

Aspects of the life cycle of the cumacean Diastylis rathkei Kröyer, the most important food item of demersal fishes in the Western Baltic Sea, were investigated from the Underwater Laboratory (UWL) Helgoland in Lübeck Bay. In August the population density was 10.1±3.6 individuals 100 cm^-2 in fine-medium sand (Md=292 m), and 3.6±2.4 individuals in coarser medium sand (Md=470 m). In both substrata, abundance values decreased until October, at each station to a different extent. Particular attention was paid to vertical migrations of D. rathkei. Plankton catches and numerous direct observations provided evidence that the pelagic phase, observed at night, is always combined with ecdysis. During short periods of high swarming and moulting activities, the population structure changed considerably: juveniles of the 3rd stage dominated in early August; thereafter they were replaced by prematures, the last juvenile stage. The first mature individuals were observed in October. Some data are given on growth rate.     

From metamorphosis to maturity in complex life cycles: equal performance of different juvenile life history pathways

Performance in one stage of a complex life cycle may affect performance in the subsequent stage. Animals that start a new stage at a smaller size than conspecifics may either always remain smaller or they may be able to "catch up" through plasticity, usually elevated growth rates. We study how size at and date of metamorphosis affected subsequent performance in the terrestrial juvenile stage and lifetime fitness of spadefoot toads (Pelobates fuscus). We analyzed capture-recapture data of > 3000 individuals sampled during nine years with mark-recapture models to estimate first-year juvenile survival probabilities and age-specific first-time breeding probabilities of toads, followed by model selection to assess whether these probabilities were correlated with size at and date of metamorphosis. Males attained maturity after two years, whereas females reached maturity 2-4 years after metamorphosis. Age at maturity was weakly correlated with metamorphic traits. In both sexes, first-year juvenile survival depended positively on date of metamorphosis and, in males, also negatively on size at metamorphosis. In males, toads that metamorphosed early at a small size had the highest probability to reach maturity. However, because very few toadlets metamorphosed early, the vast majority of male metamorphs had a very similar probability to reach maturity. A matrix projection model constructed for females showed that different juvenile life history pathways resulted in similar lifetime fitness. We found that the effects of date of and size at metamorphosis on different juvenile traits cancelled each other out such that toads that were small or large at metamorphosis had equal performance. Because the costs and benefits of juvenile life history pathways may also depend on population fluctuations, ample phenotypic variation in life history traits may be maintained.     

Survival,metabolism and growth of Ulva lactuca under winter conditions: a laboratory study of bottlenecks in the life cycle

Photosynthesis and growth in low light and survival under simulated winter conditions were studied in the freefloating green alga Ulva lactuca L., collected in Roskilde Fjord, Denmark during late autumn and maintained in stock in natural water. It adapts efficiently to low light by increasing chlorophyll concentration and light absorption and continues to grow at the lowest irradiance tested, 0.6 E m^-2 s^-1. This irradiance corresponds to minimum light requirements of deep-living marine macroalgae and phytoplankton growing under ice. The photosynthetic efficiency per unit of incident light is five-fold higher for U. lactuca grown at 1.7 E PAR m^-2 s^-1 as compared with 56.3 E m^-2 s^-1, and the efficiency per unit of light absorbed is twice as high. The maximum photosynthetic efficiency (0.051 mol C E^-1 absorbed) is similar to values for shade-adapted marine phytoplankton. U. lactuca is able to survive for two months in the dark and to resume growth immediately when transferred to light. Exposure to anoxia and sulphide gradually reduces vitality, but does not affect survival over two months. Rigorous deep freezing is detrimental to survival of U. lactuca, while field samples show that more gradual, natural freezing is not. U. lactuca is not easily fitted into one of the traditional strategy concepts. U. lactuca is a very plastic species that combines rapid growth during favourable periods (opportunism) with high survival capacity in the same type of tissue during stress periods (persistence). U. lactuca occupies a niche as a free-floating form in sedimentary coastal areas that are devoid of attached algae.     

Protracted estuarine phase in the life cycle of the marine pufferfish Torquigener pleurogramma

The present study was undertaken to elucidate the way in which the Swan Estuary in south-western Australia is used by the common blowfish Torquigener pleurogramma, a representative of the abundant and widely distributed family Tetraodontidae. T. pleurogramm were collected by beach seine and otter trawl from the Swan Estuary between February 1977 and December 1980 and between May 1984 and February 1986. While T. pleurogramma feeds on a wide variety of organisms in the estuary, the main components of its diet are polychaetes and amphipods for fish <130 mm and bivalve molluscs for larger fish. Numbers of blowfish were inversely correlated with water depth, with densities on the banks (water depth <1.5 m) sometimes reaching 5 fish m^-2, and tended to be greater at night than during the day. The density of T. pleurogramma in the shallows was positively correlated with salinity and inversely correlated with distance from the estuary mouth. Numbers increased greatly in the latter half of 1980 and 1985 as a result of the recruitment of large numbers of the 0+ age class (i.e., fish in their first year of life). Blowfish were represented by seven age classes in the estuary and attained a maximum size of 230 mm (220 g). By the end of their first and second years of life, fish had reached approximately 90 mm (14 g) and 125 mm (39 g), respectively. Sexual maturity was generally not reached until the end of the second year of life. The presence of higher gonadosomatic indices and more mature gonads in fish collected just outside than within the estuary indicate that T. pleurogramma leaves the estuary before spawning. Comparisons between lengthfrequency data, allied with information on the prevalence and intensity of gill parasites, indicate that assemblages in estuarine and neighbouring inshore waters remain distinct for many months and that growth within the estuary is faster than in inshore marine environments.     

Importance of life cycle events in the population dynamics of Gonyaulax tamarensis

Life cycle changes that allow populations of the toxic dinoflagellate Gonyaulax tamarensis Lebour to inhabit the benthos and the plankton alternately are important factors regulationg the initiation and decline of blooms in restricted embavments. When the dynamics of these estuarine populations were monitored during “bloom” and “non bloom” years, it was shown that: (1) each year, germination of benthie cysts inoculated the overlying waters during the vernal warming period, but a large residual population remained in the sediments throughout the blooms; (2) the resulting planktonic population began growth under suboptimal temperature conditions; (3) the populations developed from this inoculum through asexual reproduction until sexuality (and cyst formation) were induced; (4) encystment was not linked to any obvious environmental cue and occurred under apparently optimal conditions; and (5) an increase in the number of non-mitotic swimming cells (planozygotes, the precursors to dormant cysts) accompanied the rapid decline of the planktonic population. Thus encystment, in combination with hypothesized losses due to advection and grazing, contributed substantiatly to the decline of the vegetative cell population. We conclude that the encystment/excystment cycle temporally restricts the occurrence of the vegetative population and may not be optimized for rapid or sustained vegetative growth and bloom formation in shallow embayments. The factors that distinguish “bloom” from “non-bloom” years thus appear to be operating on the growth of the planktonic population.     

Biomass, photosynthesis and growth of Laminaria saccharina in a high-arctic fjord, NE Greenland

Biomass, photosynthesis and growth of the large, perennial brown alga Laminaria saccharina (L.) Lamour. were examined along a depth gradient in a high-arctic fjord, Young Sound, NE Greenland (74°18'N; 20°14'W), in order to evaluate how well the species is adapted to the extreme climatic conditions. The area is covered by up to 1.6-m-thick ice during 10 months of the year, and bottom water temperature is <0°C all year round. L. saccharina occurred from 2.5 m depth to a lower depth limit of about 20 m receiving 0.7% of surface irradiance. Specimen density and biomass were low, likely, because of heavy ice scouring in shallow water and intensive feeding activity from walruses in deeper areas. The largest specimens were >4 m long and older than 4 years. In contrast to temperate stands of L. saccharina, old leaf blades (2-3 years old) remained attached to the new blades. The old tissues maintained their photosynthetic capacity thereby contributing importantly to algal carbon balance. The photosynthetic characteristics of new tissues reflected a high capacity for adaptation to different light regimes. At low light under ice, or in deep water, the chlorophyll a content and photosynthetic efficiency (!) were high, while light compensation (E_c) and saturation (E_k) points were low. An E_c of 2.0 µmol photons m^-2 s^-1 under ice allowed photosynthesis to almost balance, and sometimes exceed, respiratory costs during the period with thick ice cover but high surface irradiance, from April through July. Rates of respiration were lower than usually found for macroalgae. Annual elongation rates of leaf blades (70-90 cm) were only slightly lower than for temperate L. saccharina, but specific growth rates (0.48-0.58 year^-1) were substantially lower, because the old blades remained attached. L. saccharina comprised between 5% and 10% of total macroalgal biomass in the area, and the annual contribution to primary production was only between 0.1 and 1.6 g C m^-2 year^-1.     

Assessing carbon footprint in the life cycle of accommodation services: the case of an international tourist hotel

The accommodation sector is the most demanding energy consumer among all building stock categories. This study quantifies an international tourist hotel in Taiwan to holistically estimate the greenhouse gas emissions of hotel accommodation services through a complete life cycle inventory. The study also investigates the difference between the carbon emissions of the baseline and reduction years to understand the effects of carbon emission reduction on the hotel industry. Results show that energy consumption is the main source of carbon footprint. However, the carbon emissions of other activities, such as the production and transportation of hotel amenities and laundry services, are 15.90% for the baseline year and 16.03% for the reduction year. These values are larger than the 5% cutoff rule according to PAS 2050. Thus, these factors should also be considered in assessing the carbon emissions of accommodation services. Hotel occupancy rate significantly affects carbon emissions during a one-night stay in a standard room as the functional unit. The selection of the functional unit should be considered in the hotel strategy. Although this case study involves an international tourist hotel in Taiwan, the findings and recommendations for improvements can be applied elsewhere.     

State-of-the-art applications of machine learning in the life cycle of solid waste management

● State-of-the-art applications of machine learning (ML) in solid waste (SW) is presented. ● Changes of research field over time, space, and hot topics were analyzed. ● Detailed application seniors of ML on the life cycle of SW were summarized. ● Perspectives towards future development of ML in the field of SW were discussed. Due to the superiority of machine learning (ML) data processing, it is widely used in research of solid waste (SW). This study analyzed the research and developmental progress of the applications of ML in the life cycle of SW. Statistical analyses were undertaken on the literature published between 1985 and 2021 in the Science Citation Index Expanded and Social Sciences Citation Index to provide an overview of the progress. Based on the articles considered, a rapid upward trend from 1985 to 2021 was found and international cooperatives were found to have strengthened. The three topics of ML, namely, SW categories, ML algorithms, and specific applications, as applied to the life cycle of SW were discussed. ML has been applied during the entire SW process, thereby affecting its life cycle. ML was used to predict the generation and characteristics of SW, optimize its collection and transportation, and model the processing of its energy utilization. Finally, the current challenges of applying ML to SW and future perspectives were discussed. The goal is to achieve high economic and environmental benefits and carbon reduction during the life cycle of SW. ML plays an important role in the modernization and intellectualization of SW management. It is hoped that this work would be helpful to provide a constructive overview towards the state-of-the-art development of SW disposal.     

Direct and indirect effects of pesticides on a benthic grazer during its life cycle

Background

Macroinvertebrates in aquatic ecosystems are repeatedly exposed to pesticides during their life cycle. Effects of consecutive exposure during different life stages and possible synergistic effects are not addressed in the standardized hazard assessment. The present study investigated two environmentally relevant exposure scenarios in batch (microcosm) and artificial indoor stream (mesocosm) experiments using the larvae of the mayfly Rhithrogena semicolorata (grazer) and natural aufwuchs. Grazers were analysed regarding growth, physiological condition, and drift behaviour, while the aufwuchs was analysed in terms of biomass using the particulate organic carbon as well as the chlorophyll a content. The aim was to reveal direct and indirect effects of an herbicide exposure during autumn on juvenile grazers and an insecticide exposure during spring on semi-juvenile grazers.

Results

Direct and indirect effects were found in both exposure scenarios at environmentally relevant concentrations. In the herbicide exposure scenario with terbutryn, clear direct effects on the aufwuchs community with a LOEC of 0.38 µg L^?1 were found. Effect levels of grazers due to indirect effects were equal, with the overnight drift being the most sensitive grazer endpoint. In the insecticide exposure scenario, clear lethal and sub lethal effects of lambda-cyhalothrin were evident. Derived LC₅₀ values for the artificial indoor stream and batch experiment were 2.42 µg g^?1 OC (69 days) and 1.2 µg g^?1 OC (28 days), respectively. Sub lethal effects in terms of increased drift as well-reduced growth and triglyceride levels were found at concentrations of 1.4 and 0.09 µg g^?1 OC (LOECs). These results were confirmed by the batch experiment, which revealed effect values in the similar range. Finally, a clear indirect effect of the insecticide on the aufwuchs was evident in the batch experiment with an LOEC at 0.9 µg g^?1 OC.

Conclusion

Toxicity Exposure Ratios calculated with the derived effect values indicate a risk for the investigated grazer by both pesticides. Moreover, observed indirect effects during the herbicide exposure seem to be able to affect the grazers during a second exposure with an insecticide, due to reduced physiological conditions. We suggest further research with time-shifted exposure scenarios to gain a better understanding of the complex interactions of pesticides with the life cycle and the food webs of macroinvertebrates.

     

The representation of cyanobacteria life cycle processes in aquatic ecosystem models

Two simplified versions of a numerical life cycle model for diazotrophic cyanobacteria (of the order Nostocales) are developed and evaluated. Both consider two-life cycle stages, one growing, nitrogen-fixing stage and one stage that combines the resting, germinating and vegetative stages. The versions differ in the vertical resolution of the non-diazotrophic stage: version 1 collects the biomass in one layer at the bottom, version 2 considers sinking and rising of biomass explicitly. The results of the two versions are compared with a complex cyanobacteria life cycle model which describes four different life cycle stages each with two internal quotas for energy and nitrogen. The two simplified approaches show a good agreement with respect to the main characteristics of cyanobacteria dynamics (timing and duration of blooms, magnitude of nitrogen fixation, interannual variability). Our model study shows that both simplified approaches are suitable to be implemented into three-dimensional coastal or lake models.