STOICHIOMETRIC RESPONSES OF PHYTOPLANKTON SPECIES TO THE INTERACTIVE EFFECT OF NUTRIENT SUPPLY RATIOS AND GROWTH RATES1

Three species of phytoplankton, Rhodomonas sp., Phaeodactylum tricornutum Bohlin, and Isochrysis galbana Parke, were cultivated in semicontinuous culture to analyze the response of carbon (C):nitrogen (N):phosphorus (P) stoichiometry to the interactive effect of five N:P supply ratios and four growth rates (dilution rates). The relationship between cellular N and P quotas and growth rates fits well to both the Droop and Ågren’s functions for all species. We observed excess uptake of both N and P in the three species. N:P biomass ratios showed a significant positive relationship with N:P supply ratios across the entire range of growth rates, and N:P biomass ratios converged to an intermediate value independent of N:P supply ratios at higher growth rates. The effect of growth rates on N:P biomass ratios was positive at lower N:P supply ratios, but negative at higher N:P supply ratios for both Rhodomonas sp. and I. galbana, while for P. tricornutum this effect was negative at all N:P supply ratios. A significant interactive effect of N:P supply ratios and growth rates on N:P biomass ratios was found in both Rhodomonas sp. and P. tricornutum, but not in I. galbana. Our results suggest that Ågren’s functions may explain the underlying biochemical principle for the Droop model. The parameters in the Droop and Ågren’s functions can be useful indications of algal succession in the phytoplankton community in changing oceans.     

Microalgae for phosphorus removal and biomass production: a six species screen for dual‐purpose organisms

Microalgae biofuel production can be feasible when a second function is added, such as wastewater treatment. Microalgae differ in uptake of phosphorus (P) and growth, making top performer identification fundamental. The objective of this screen was to identify dual‐purpose candidates capable of high rates of P removal and growth. Three freshwater – Chlorella sp., Monoraphidium minutum sp., and Scenedesmus sp. – and three marine – Nannochloropsis sp., N. limnetica sp., and Tetraselmis suecica sp. – species were batch cultured in 250 mL flasks over 16 days to quantitate total phosphorus (TP) removal and growth as a function of P loads (control, and 5, 10, and 15 mg L^?1 enrichment of control). Experimental design used 100 μmol m^?2 s^?1 of light, a light/dark cycle of 14/10 h, and no CO₂ enrichment. Phosphorus uptake was dependent on species, duration of exposure, and treatment, with significant interaction effects. Growth was dependant on species and treatment. Not all species showed increased P removal with increasing P addition, and no species demonstrated higher growth. Nannochloropsis sp and N. limnetica sp. performed poorly across all treatments. Two dual‐purpose candidates were identified. At the 10 mg L^?1 treatment Monoraphidium minutum sp. removed 67.1% (6.66 mg L^?1 ± 0.60 SE) of TP at day 8, 79.3% (7.86 mg L^?1 ± 0.28 SE) at day 16, and biomass accumulation of 0.63 g L^?1 ± 0.06 SE at day 16. At the same treatment Tetraselmis suecica sp. removed 79.4% (6.98 mg L^?1 ± 0.24 SE) TP at day 8, 83.0% (7.30 mg L^?1 ± 0.60 SE) at day 16, and biomass of 0.55 g L^?1 ± 0.02 SE at day 16. These species merit further study using high‐density wastewater cultures and lipid profiling to assess suitability for a nutrient removal and biomass/biofuel production scheme.     

Pipunculidae (Diptera) of the 1934 Swedish Expedition to Burma

Hardy, D. E. (Department of Entomology, University of Hawaii, Honolulu, Hi., USA.) Pipunculidae (Diptera) of the 1934 Swedish expedition to Burma. Zool. Scripta 1(3–4): 121–138, 1972.–The collection of Pipunculidae made in Burma by Rene Malaise contained approximately forty species in five genera and four subgenera and is probably a thorough sampling of the species which occur in the Kambaiti area of N.E. Burma. Eleven new species are being described: Dorylomorpha latifrons sp.n., D. stenozona sp.n., Pipunculus (Cephalops) dolosus sp.n., P. (Cephalops) fimbriatus sp.n., P. (Cephalops) validus sp.n., P. (Cephalosphaera) reduncus sp.n., P. (Cephalosphaera) tingens sp.n., P. (Eudorylas) burmanicus sp.n., P. (Eudorylas) colossus sp.n., P. (Eudorylas) giganteus sp.n., and P. (Eudorylas) malaisei sp.n. Several other species, probably new ones, are indicated but not being described until further specimens can be studied. The majority of the species are new records for Burma.     

A survey of epiphytic dinoflagellates from the coastal waters of the island of Hawai‘i

Three hundred and sixty-nine macroalgal and non-algal samples were collected from six coastal sites around the island of Hawai‘i on a biweekly basis over a 1-year period to ascertain (1) the presence of potentially toxigenic benthic dinoflagellates, and (2) substrate and environmental preferences of the dinoflagellates. Twenty-six genera/species of dinoflagellates were encountered including the (potentially) toxigenic species Amphidinium sp., Coolia monotis, Gambierdiscus sp., Ostreopsis ovata, Prorocentrum concavum, Prorocentrum hoffmannianum, Prorocentrum lima, and Prorocentrum mexicanum. Twenty of the species are being reported for the first time as present in Hawaiian coastal waters. There was some evidence of macroalgal host preference (e.g., C. monotis on Tolypiocladia glomerulata), although host morphology preferences was greater (e.g., Gambierdiscus sp., and P. lima on filamentous turfs; O. sp. 1 on sheet-like macroblades). While some dinoflagellate groups were significantly correlated with nutrient concentrations (e.g., total dinoflagellates with nitrate + nitrite and phosphate concentrations), others were not (e.g., Gambierdiscus sp., Prorocentrum emarginatum, P. lima, and Sinophysis microcephalus). The presence of several potentially toxigenic dinoflagellate species in Hawai‘i merits future study on possible impacts of these dinoflagellates on coastal food webs and human health.     

Settlement, growth and survival of abalone, Haliotis discus hannai, in response to eight monospecific benthic diatoms

The settlement, early growth and survival of the larval abalone Haliotis discus hannai in response to eight monospecific benthic diatoms were examined in the laboratory. Postlarvae showed active settling and feeding behaviour in all diatom species and in naturally occurring diatoms. Larval settlement rates differed significantly between experimental substrata after 24 h and 48 h. Nitzschia sp. (96.67 %), Hantzschia amphioxys var. leptocephala (95.00 %) and Navicula seminulum (90.00 %) strongly induced larval settlement of H. discus hannai. Postlarvae could feed on benthic diatoms (< 36 μm in shell length) with both weak and strong adhesion on the 4th day after settlement. Greatest growth (shell length) occurred on Nitzschia sp. (786.84 μm ± 2.50 SE and 773.09 μm ± 2.09 SE). Survival of postlarvae was also greatest on Nitzschia sp. (95.33 % ± 1.45 SE). These results indicate the effectiveness of Nitzschia sp., H. amphioxys var. leptocephala, N. seminulum, Rhaphoneis surirella and Navicula corymbosa as single species over natural diatoms in larval settlement and postlarvae growth of H. discus hannai. Thus, Nitzschia sp. has the best potential diet for larval settlement and postlarvae growth of H. discus hannai. H. amphioxys var. leptocephala and N. seminulum can be used as cues to induce larvae settlement, and R. surirella and N. corymbosa can be used as food for growing postlarval.     

Linking elements to biochemicals: effects of nutrient supply ratios and growth rates on fatty acid composition of phytoplankton species

Three species of marine phytoplankton, Rhodomonas sp., Isochrysis galbana Parke, and Phaeodactylum tricornutum Bohlin, were cultivated in semicontinuous cultures to test biochemical responses (fatty acids; FAs) to five nitrogen (N):phosphorus (P) supply ratios and four growth rates (dilution rates). The characteristic FA profile was observed for each algal species (representing particular algal class), which remained relatively stable across the entire ranges of N:P supply ratios and growth rates. For all species, significant direct effects of N:P supply ratios on FAs were found at lower growth rates. The highest saturated and monounsaturated fatty acid (SFA and MUFA) contents were observed under N deficiency at the lowest growth rate in all three species, while responses of polyunsaturated fatty acids (PUFAs) revealed no consistent pattern. Total FAs (and SFAs and MUFAs) in all species showed significant negative correlations with N cell quota (Q_N) under N deficiency, but PUFAs had species‐specific correlations with Q_N. The results show that characteristic FA profiles of algal genus or species (representing particular algal classes) underlie fluctuations according to culture conditions. The significant correlation between FAs and Q_N under N deficiency suggests that elemental and biochemical limitation of phytoplankton should be considered mutually as determinants of food quality for zooplankton in marine ecosystems.     

Lake Kinneret phytoplankton: Response to N and P enrichments in experiments and in nature

A series of water samples from Lake Kinneret was supplemented with 100 µM N (as NH₄ or as NO₃ and/or 10 µM orthophosphate-P. The yield of phytoplankton both as chlorophyll and in cell numbers of major species was determined after a two-week incubation. During these experiments, some of the algae present initially never multiplied (e.g. Peridinium and Peridiniopsis spp. Cryptomonas spp., Rhodomonas spp. and Crysochromulina parva); others e.g. Anomoeoneis exilis, Synedra sp., Chlamydomonas sp., Elakatothrix gelatinosa), undetected in the original sample, grew out during the incubation. Chlorophyte species (the majority of commonly observed forms in the lake) responded most readily to added nutrients.The results of these enrichment experiments were related to the long-term record of phytoplankton populations observed in the lake and suggest that through summer and fall, when ambient levels of both P and N are minimal, P was generally, but not always, the most limiting nutrient for algal growth. In the spring, after the decline of the Peridinium bloom, P appeared to be limiting the growth of Chlorophyta. Although most algal species grew equally well on NH₄ or NO₃, some species appeared to respond preferentially either to the former (Coelastrum, Chodatella) or to the latter (Chroococcus, Anomoeoneis) source of N.     

Growth and uptake kinetics of phosphate by benthic microalga Nitzschia sp. isolated from Hiroshima Bay,Japan

In the present study, we experimentally investigated the phosphate uptake kinetics of benthic microalga Nitzschia sp. isolated from Hiroshima Bay, Japan. The maximum uptake rate (ρ_max) obtained by short‐term experiments was 6.84 pmol cell^?1 h^?1 for phosphate. The half‐saturation constant for uptake (K_S) was 61.2 µmol cell^?1 h^?1. Both the ρ_max and Ks of this species were extremely high, suggesting that Nitzschia sp. is adapted to benthic environments, where nutrient concentrations are much higher than in the water column. The specific maximum growth rate (µ'_max) and minimum cell quota (Q₀) for the P‐limited condition, obtained by a semi‐continuous growth experiment, were 0.48 day^?1 and 0.045 pmol cell^?1, respectively. It is concluded that Nitzschia sp. could be a ‘storage strategist’ species, meaning it adapts so as to minimize the influence of fluctuations in phosphate conditions resulting from the change in redox conditions of sediment due to bioturbation.     

Survival and metabolism of the harpacticoid copepod Thompsonula hyaenae (Thompson) fed on different diatoms

Survival times and oxygen consumption rates have been determined for a benthic harpacticoid copepod, Thompsonula hyaenae (Thompson), when fed different algal diets. Nauplii and adults lived slightly longer on a diet of Navicula sp. than did those fed N. pelliculosa or a mixture of both naviculoid species. Mean numbers of harpacticoids hatched were significantly higher in cultures of N. pelliculosa. Metabolic rates of non-gravid females fed for one week on N. sp. were significantly lower than those fed N. pelliculosa or the mixture. There was no significant difference in oxygen uptake between animals fed N. pelliculosa and those fed the mixed culture. The smaller size and lower food energy content of N. pelliculosa are reflected in the higher respiratory rates of animals led this diatom species.Based on a thesis submitted in partial fulfillment of the M.S. degree in Marine Science at the University of South Carolina. Belle W. Baruch Institute for Marine Biology and Coastal Research Contribution No. 114. Research supported by the Oceanography Section, National Science Foundation, NSF Grant DES72-01573 A01.     

Empirical models for predicting the excretion of nutrients (N and P) by aquatic metazoans: taxonomic differences in rates and element ratios

1. We developed empirical models for predicting the release of nutrients [nitrogen (N) and phosphorus (P)] by aquatic metazoans (zooplankton, mussels, benthic macroinvertebrates and fish). 2. The number of species represented in each model ranged from 9 to 74 (n = 40 – 1122), organism dry mass from 1 × 10^?5 to 8 × 10⁴ mg and water temperature from ?1.8 to 32 °C for all models. Organisms were from marine and freshwater (both lotic and lentic) environments. 3. Rates and ratios of nutrient excretion were modelled and intra‐ and intertaxon differences in excretion were examined. Rates of N and P excretion were not significantly different between marine and freshwater species within the same taxon (e.g. zooplankton). However, rates of excretion (as a function of organism dry mass and water temperature) were significantly different among different orders of zooplankton, mussels and fish. However, excretion of N was similar among different orders of benthic macroinvertebrates. 4. Detritivorous fish excreted both N and P at rates greater than all other taxa; whereas mussels excreted N and P generally at rates less than other taxa. There were no significant differences in the rate of N and P excretion between zooplankton and fish (i.e. the allometry of N and P excretion was similar between zooplankton and fish). 5. Molar N : P ratios of nutrients excreted increased with increasing organism dry mass for each group of metazoans, except for zooplankton and detritivorous fish (where N : P ratios declined with increasing organism dry mass). Molar N : P ratios in the excretions of aquatic metazoans were generally below the Redfield ratio of 16:1. 6. We examined the influence of variable abundance of zooplankton, benthic macroinvertebrates and fish on assemblage excretion rates. Rates of N and P excretion were calculated by applying our models to metazoan biomass and abundance data over seven consecutive years in two oligotrophic lakes. Rates of N and P excretion (g ha^?1 day^?1) increased linearly with increasing assemblage biomass (kg ha^?1). However, rates of N and P excretion were significantly and negatively correlated with the relative abundance of fish and positively correlated with the relative abundance of zooplankton.     

Colonization and succession of benthic macroinvertebrates in Arcadia Lake,a South-Central USA reservoir

Colonization and succession of benthic macroinvertebrates in Arcadia Lake, an urban reservoir, were studied for four years. Physicochemical conditions including water temperature, dissolved oxygen concentrations, pH, specific conductance, and Secchi disc depth were also recorded. Colonization of the reservoir occured fairly rapidly through a sequence of three invasions. The first, and most significant, colonists were primarily facultative species already present in streams and ponds that were inundated by the impoundment. Later arrivals tended to be limnophilic species that probably came from other bodies of water. Of 30 species encountered in a pre-impoundment collection, only six were still present three years following impoundment. Thirty-three additional benthic macroinvertebrates species invaded the area following impoundment. Dominant taxa in the reservoir included Dero nivea, Limnodrilus sp., Chaoborus punctipennis, Chironomus sp., and Procladius sp. Pollutants accumulating in this urban reservoir, including metals and pesticides, and siltation probably have kept benthic populations relatively low and possibly reduced potential species diversity.     

The Psyllids (Homoptera: Psylloida) of Alaska

A key is provided for the identification of the thirty-eight psyllid species recorded from Alaska. Additional notes on host plant and distribution are given for each species. The species are: Aphalara manitobaensis Cald.,A.nigra Cald., Craspedolepta alaskensis (Ash.), C.nebulosa (Zett.) ssp. kincaidi (Ash.), C. schwarzi (Ash.), C.subpunctata (Förster), Psylla alaskensis Ash., P.betulaenanae Oss., P.breviata Patch, P.fibulata Crawf., P.floccosa Patch, P.galeaformis Patch, P.haliaeeti sp.nov., P.hamata Tuthill, P.highwoodensis sp.nov., P.jenseni sp.nov., P.kananaskensis Hod., P.ledi Flor., P.longiforceps sp.nov., P.minor Crawf., P.macleani sp.nov., P.myrtilli Wag. ssp. canadensis Hod., P.palmeni Löw, P.phlebophyllae sp.nov., P.rara Tuthill, P.rufipennis sp.nov., P.sinuata Crawf., P.striata Patch, P.stricklandi Crawf., P.toolikensis sp.nov., P.zaecevi Sulc, Trioza albifrons Crawf., Trioza artica sp.nov., T.atkasookensis sp.nov., T.incerta Tuthill, T.salicivora Reut. (=T.maura auctt. N.Amer.), T.stylifera Patch, Trioza sp.nov. (undescribed). All the newly described species were collected on Salix. The Alaskan fauna is made up of four major components: 1, true Arctic species; 2, Arctic/subarctic species; 3, subarctic/alpine species; 4, northern forest zone species. Eight of the Alaskan psyllids exhibit an holarctic distribution and there is a strong faunal affinity with similar areas in northern Scandinavia: the same four genera recur throughout the northern holarctic. There is strong circumstantial evidence that certain psyllid species are parthogenetic over part of their range, particularly in arctic/alpine situations.     

The amino acid and gross composition of marine diatoms potentially useful for mariculture

The amino acid and gross compositions of three benthic diatoms (Cylindrotheca fusiformis Reimann and Lewin, Navicula jeffreyi Hallegraeff et Burford and Nitzschia closterium (Ehr. W. Smith) and three chain-forming diatoms (Lauderia annulata Cleve, Skeletonema costatum (Greville) Cleve and a tropical Skeletonema sp. (CS-252)), were determined during late-logarithmic growth phase.Four of the six species were rich in protein, ranging from 31% (S. costatum) to 38% (N. closterium) of the dry weight, and contained 4.9 to 6.5% carbohydrate and 9.4 to 18% ash. The other two species, C. fusiformis and L. annulata contained only 16% protein but had nearly twice the total carbohydrate (11 to 12%) and two to three times the ash (29 to 35%) of the other species. All species contained a similar percentage of lipid (18 to 20%), and a high protein quality based on their total amino acid composition.The usefulness of these diatoms for mariculture will be determined by growth rates, gross composition and acceptability to the animal. N. closterium had the fastest growth rates of the benthic mat-forming diatoms, it was rich in protein, and it may be a good candidate for abalone culture. The two Skeletonema spp. had the fastest growth rates of the chain-forming diatoms, and are already widely used for prawn larval culture in Australia. Feeding trials are now necessary to confirm the high nutritional value of these diatom species for specific animals.     

PRODUCTION AND NUTRIENT REMOVAL BY PERIPHYTON GROWN UNDER DIFFERENT LOADING RATES OF ANAEROBICALLY DIGESTED FLUSHED DAIRY MANURE1

Growing algae to scrub nutrients from manure presents an alternative to the current practice of land application and provides utilizable algal biomass as an end product. The objective of this study was to assess algal growth, nutrient removal, and nitrification using higher light intensities and manure loading rates than in the previous experiments. Algal turfs, with periphyton mainly composed of green algal species, were grown under two light regimes (270 and 390 μmol photons·m^?2· s^?1) and anaerobically digested flushed dairy manure wastewater (ADFDMW) loading rates ranging from 0.8 to 3.7 g total N and 0.12 to 0.58 g total P·m^?2·d^?1. Filamentous cyanobacteria (Oscillatoria spp.) and diatoms (Navicula, Nitzschia, and Cyclotella sp.) partially replaced the filamentous green algae at relatively high ADFDMW loading rates and more prominently under low incident light. Mean algal production increased with loading rate and irradiance from 7.6±2.71 to 19.1±2.73 g dry weight· m^?2·d^?1. The N and P content of algal biomass generally increased with loading rate and ranged from 2.9%–7.3% and 0.5%–1.3% (by weight), respectively. Carbon content remained relatively constant at all loading rates (42%–47%). The maximum removal rates of N and P per unit algal biomass were 70 and 13 mg·g^?1 dry weight·m^?2·d^?1, respectively. Recovery of nutrients in harvested algal biomass accounted for about 31%–52% for N and 30%–59% for P. Recovery of P appeared to be uncoupled with N at higher loading rates, suggesting that algal potential for accumulation of P may have already been saturated. It appears that higher irradiance level enhancing algal growth was the overriding factor in controlling nitrification in the algal turf scrubber units.     

Feeding in adult females of Argyrodiaptomus furcatus (Sars,1901), Copepoda-Calanoida,of Lobo Reservoir (Broa), São Carlos,São Paulo,Brazil

The aim of this work was to study the feeding process of Argyrodiaptomus furcatus (Copepoda-Calanoida) in the Lobo Reservoir (São Carlos, SP, Brazil). Non-ovigerous adult females and the ¹⁴C technique were used to measure filtration and assimilation rates. The diet contained the following phytoplankton species: Chlamydomonas sp., Ankistrodesmus gracilis, Melosira italica, Scenedesmus quadricauda and Chlorella zoofingensis.The experiments were carried out using unialgal and mixed cultures during 2-, 4- and 6-h periods. The results of the filtration and assimilation rates were compared.The data obtained by statistical tests showed the highest assimilation rate in Argyrodiaptomus furcatus fed Chlamydomonas sp. in both culture types. However, Chlorella zoofingensis and Scenedesmus quadricauda were the most filtered species in unialgal and mixed cultures, respectively. A higher filtration rate was observed for the 2-h period than for the 4- and 6-h periods.Culture agent was also important. Higher assimilation and filtration rates were obtained during the log phase of Chlamydomonas sp. growth than during the stationary phase.     

Revision of the <Emphasis Type="Italic">Nepalomyia pallipilosa</Emphasis> species group (diptera,dolichopodidae, Peloropeodinae)

The genus Nepalomyia is the largest genus in the subfamily Peloropeodinae, with 47 described species. In the present paper the Nepalomyia pallipilosa species group is established for the following three described species and seven new species: Nepalomyia biseta sp. n., N. emeiensis sp. n., N. guangxiensis Zhang et Yang, N. liui sp. n., N. pallipilosa (Yang et Saigusa), N. ruiliensis Wang et Yang, N. sichuanensis sp. n., N. ventralis sp. n., N. yangi sp. n. and N. zengchengensis sp. n. Information on their distribution is also given or updated.     

Ecology and production of invertebrates in a Canadian coldwater spring-springbrook system

Valley Spring is a hardwater rheocrene consisting of a single point issue and a springbrook some 60 m long. The fauna consists of > 60 taxa, with insects and mites predominating. During 1985–86, benthic densities varied both along the springbrook and at single stations over time (range 58 to 756 animals 900 cm⁻²). A clear longitudinal zonation of many of the major taxa occurred with the Diptera tending to be more abundant downstream, the Plecoptera and Acari more abundant upstream, and the Copepoda and Bivalvia most abundant in mid- and downstream sections. The Gastropoda and Trichoptera occurred throughout the system although, in the case of the latter, there were distributional differences at the species level (e.g. Diplectrona modesta downstream, Parapsyche apicalis and Lepidostoma vernale upstream). Life histories varied between major species and were grouped into: (A) those species in which there was a wide range of larval sizes for most of the year, with no easily discernible temporal succession of cohorts, e.g. L. vernale, P. apicalis, Sialis sp., Dixa sp., Metriocnemus sp., Trissopelopia sp., Micropsectra sp. and Mucronothrus nasalis (the generation time of species in this group ranged from < 1 year to > 2 years); and (B) those species in which there was a clear pattern of larval growth, with obvious temporal succession of cohorts, e.g. D. modesta, Nemoura trispinosa and Hyalella azteca (all of these species were univoltine). Differences between the “adaptive strategies” of these two life history types are discussed. Total secondary production in Valley Spring in 1985–86 was estimated to be 913.2 g wet wt yr⁻¹. Production upstream was more than twice that downstream (11.21 and 4.01 g wet wt m⁻² yr⁻¹, respectively). The three most abundant species of caddisfly together contributed > 30% of the total production, the stonefly N. trispinosa contributed > 17%, while the chironomids accounted for >16% of production at downstream stations but only 3% upstream.     

Optimization of growth conditions and fatty acid analysis for three freshwater diatom isolates

Diatoms are a group of highly abundant and diverse aquatic algae species. They contain high lipid content along with many bioactive compounds that can be exploited for biotechnological applications. Despite these attractive attributes, diatoms are underrepresented in production projects due to difficulties in their cultivation. To optimize the growth of three freshwater diatom isolates, Cyclotella sp., Synedra sp. and Navicula sp., an orthogonal assay on N, P, Si and Fe, as well as temperature and pH, was designed using traditional single‐factor tests. We also studied the effect of using nanosilica as an alternate Si source on growth and found that the diatom isolates studied achieved their highest growth rates under different combinations of nutrient and environmental conditions. Silica had the greatest influence on growth, followed by phosphate and iron. The optimized growth conditions for Synedra sp. were N: 30 mg L^?1, P: 3 mg L^?1, Si: 14.8 mg L^?1, Fe: 0.448 mg L^?1, temperature 25°C and pH 8. For Navicula sp.: N: 20 mg L^?1, P: 2.5 mg L^?1, Si: 19.7 mg L^?1, Fe: 0.112 mg L^?1, temperature 30°C and pH 7.5–8. For Cyclotella sp.: N: 20 mg L^?1, P: 2.5 mg L^?1, Si: 19.7 mg L^?1, Fe: 0.448 mg L^?1, temperature 30°C and pH 7.5–8. Nano silica negatively affected growth in Navicula sp. and Cyclotella sp., but no such effect was observed in Synedra sp. Fatty acid profiling showed C16:0, C16:1(n ? 7), C18:0 and C20:5(n ? 3) as major fatty acids, with no significant differences in fatty acid methyl ester profiles between traditional and modified media. This work gives us a new insight into the growth requirements of freshwater diatom species, which are less studied than marine species.     

Integration of consumer-targeted microalgal production with marine fish effluent biofiltration – a strategy for mariculture sustainability

EU regulations recommend effluent treatment and nutrient recycling for aquaculture sustainability, so a study was undertaken to provide base-line data for the integration of commercial fish-farm effluents with the production of microalgae. The project relates to a specific bivalve consumer (Tapes decussatus) and biofiltration. Effluent inorganic nutrient composition was assessed and evaluated as culture media for Phaeodactylum tricornutum, Tetraselmis suecica and Tetraselmis sp. Optimization of the microalgal compartment included studies on preparation of a simple medium, nutrient or dilution rate manipulation and nutrient removal. Cell harvest was increased chiefly by N correction (6-fold for Tetraselmis sp.) and semi-continuous or continuous operation (by a factor of 3 to 11). Nutrient removal efficiency was high for ammonium and nitrite-nitrogen (80–100%), depending on species, nutrient ratio (Si correction for P. tricornutum) and culture regime for nitrate (41–100%) or phosphorus (21–99%). Data obtained under cyclostat cultivation (yields of 1.38 and 0.50×10⁶ P. tricornutum or Tetraselmis sp. cells mL⁻¹ d⁻¹ and nutrient uptake rates of 2.32 mg N L⁻¹ d⁻¹ and 0.96 mg P L⁻¹ d⁻¹) were used to show clam production and simultaneous wastewater treatment possibilities through the proposed fish-microalgae-clam integrated aquaculture system.