Polar extracts of the brown alga Fucus vesiculosus (L.) reduce assimilation efficiency but do not deter the herbivorous isopod Idotea baltica (Pallas)

Plant secondary metabolites provide resistance against herbivory if they are capable of decreasing herbivore performance or deterring feeding. Here we test the effects of phlorotannin-containing polar extracts from the brown alga Fucus vesiculosus on the assimilation efficiency and feeding preferences of the herbivorous isopod Idotea baltica. We test the effects separately for each sex of the isopod to test the hypothesis that the digestive efficiencies of the sexes may have diverged. Phlorotannin-containing polar extracts were incorporated into an agar-based artificial food in varying amounts. We also varied the quality of the food, using high-quality food containing animal proteins and low-quality food containing only algal material. The total assimilation efficiency as well as the assimilation efficiencies of carbon and nitrogen decreased with an increasing concentration of phlorotannin-containing extracts. The negative effects on carbon and nitrogen assimilation were higher when extracts were incorporated in the high-quality food. Females were consistently more efficient than males in all assimilation measures; there were no interactions between sex and food quality or phlorotannin concentration, suggesting that the digestive efficiency of the sexes had diverged but that the two sexes responded similarly to phlorotannin enriched artificial food. Although phlorotannin-containing extracts were harmful to performance, they did not deter feeding in preference tests. On the contrary: the isopods preferred the food containing more phlorotannins, suggesting that phlorotannins may act as cues in host recognition. Thus phlorotannins were inefficient deterrents, and I. baltica seems to be adapted to utilizing phlorotannin-containing foods despite their detrimental effects on assimilation. We suggest that F. vesiculosus provides a predation refuge and temporal constancy in availability for I. baltica, both of which select for the ability to utilize it as a food. Phlorotannin-containing polar extracts from F. vesiculosus are still harmful digestibility reducers, and may thereby prevent complete specialization and generate selection for utilization of a wider host range.     

Evidence for consumer regulation of biofilm–nutrient interactions among hardwater streams (Pennsylvania, USA)

Experimental studies evaluating the simultaneous effects of consumers, nutrients, and other biotic/abiotic factors on intact, natural food webs are rare, particularly among ecosystems of varying trophic conditions. We conducted a series of in situ studies that used nutrient-diffusing substrata with nitrogen (N) and phosphorus (P) concentrations in a full factorial design in three temperate, limestone streams in Pennsylvania across a trophic gradient (mesotrophic, eutrophic, and hypereutrophic streams). We assessed differences in algal and macroinvertebrate biomass, taxonomic composition, and functional groups relative to amended nutrients across the trophic gradient; as such, these results facilitated predictions about regulators of food web structure. All factors varied significantly among the streams (e.g., algal biomass P = 0.005, macroinvertebrate biomass P < 0.001, algal diversity P = 0.006, macroinvertebrate diversity P < 0.001, algal group P < 0.001, macroinvertebrate guilds P < 0.001); the streams, however, did not exhibit simple responses to nutrient amendment. Algal and macroinvertebrate biomass and diversity responded greatest in the mesotrophic stream while grazing seemed to be a strong factor preventing algal nutrient response in the eutrophic and hypereutrophic streams. Brillouin’s Evenness Index was most influenced by nutrient amendment (nutrient effect on algae and macroinvertebrates P = 0.021). As such, we concluded that biomass and diversity were mediated by complexity within intermediate trophic levels.     

Organically Grown Food Provides Health Benefits to Drosophila melanogaster

The “organic food” market is the fastest growing food sector, yet it is unclear whether organically raised food is nutritionally superior to conventionally grown food and whether consuming organic food bestows health benefits. In order to evaluate potential health benefits of organic foods, we used the well-characterized fruit fly Drosophila melanogaster as a model system. Fruit flies were raised on a diets consisting of extracts of either conventionally or organically raised produce (bananas, potatoes, raisins, soy beans). Flies were then subjected to a variety of tests designed to assess overall fly health. Flies raised on diets made from organically grown produce had greater fertility and longevity. On certain food sources, greater activity and greater stress resistance was additionally observed, suggesting that organic food bestows positive effects on fly health. Our data show that Drosophila can be used as a convenient model system to experimentally test potential health effects of dietary components. Using this system, we provide evidence that organically raised food may provide animals with tangible benefits to overall health.     

Effects of No. 2 Fuel Oil, Nigerian Crude Oil, and Used Crankcase Oil on Attached Algal Communities: Acute and Chronic Toxicity of Water-Soluble Constituents

Water extracts of a no. 2 fuel oil, a Nigerian crude oil, and used crankcase oil were examined for their effects on algal communities in experiments lasting several weeks conducted under near-natural conditions. No. 2 fuel oil extracts depressed algal biomass (chlorophyll a) and resulted in blue-green algal (cyanobacterial) dominance and decreased diatom occurrence. Changes in concentrations of chlorophyll c, which was specific for diatoms in this work, and phycocyanin, which was specific for blue-green algae, confirmed the observations. Used crankcase oil extracts also depressed biomass, but Nigerian crude extracts did not, and both these extracts had less effect on community composition than did no. 2 fuel oil extracts. Photosynthetic ¹⁴C incorporation was both stimulated and depressed by exposure to extracts with hydrocarbon concentrations 0.038 to 0.124 mg/liter. Short-term exposure to higher concentrations (1.17 to 15.30 mg of hydrocarbons per liter) of no. 2 fuel oil extracts depressed photosynthetic ¹⁴C incorporation by Vaucheria-dominated communities in all tests but one. Toxicity was greater from extracts prepared in the light than from extracts prepared in the dark.     

Anaerobic digestates are useful nutrient sources for microalgae cultivation: functional coupling of energy and biomass production

We investigated the extent to which nitrogenous and phosphorus nutrients from liquid anaerobic digestates could be recycled for photosynthetic growth of a microalga, Scenedesmus sp. AMDD. Digestates recovered from the anaerobic digestion of cow manure and swine manure and a co-digestion of swine manure and algal biomass were diluted in distilled water and used for algal growth with and without supplemental CO₂ addition. Nutrient assimilation and final biomass yield were retarded in all but the swine manure/algae co-digestate cultures supplemented with high CO₂. Swine manure digestate cultures supplemented with the typical complement of micronutrients normally added with a commonly used growth medium or with Fe/EDTA failed to grow any better than unamended controls. When the culture medium was prepared by blending swine manure digestate with 25 or 50 % algal biomass digestate, diluting it with lake water or by supplementing with magnesium, nutrient assimilation and final algal biomass yields were maximized, indicating that magnesium was critically limiting for algal growth in swine manure digestates. Magnesium amendment thus appears to be essential if nutrients from swine manure digestates are recycled for algal growth. No such requirement is necessary for recycling nutrients from digestates generated wholly or in part from algal biomass.     

Two-stage heterotrophic and phototrophic culture strategy for algal biomass and lipid production

A two-stage heterotrophic and phototrophic culture strategy for algal biomass and lipid production was studied, wherein high density heterotrophic cultures of Chlorellasorokiniana serve as seed for subsequent phototrophic growth. The data showed growth rate, cell density and productivity of heterotrophic C.sorokiniana were 3.0, 3.3 and 7.4 times higher than phototrophic counterpart, respectively. Hetero- and phototrophic algal seeds had similar biomass/lipid production and fatty acid profile when inoculated into phototrophic culture system. To expand the application, food waste and wastewater were tested as feedstock for heterotrophic growth, and supported cell growth successfully. These results demonstrated the advantages of using heterotrophic algae cells as seeds for open algae culture system. Additionally, high inoculation rate of heterotrophic algal seed can be utilized as an effective method for contamination control. This two-stage heterotrophic phototrophic process is promising to provide a more efficient way for large scale production of algal biomass and biofuels.     

Comparative feeding ecology of two herbivorous damselfishes (Pomacentridae: Teleostei) from the Gulf of California,Mexico

Two species of benthic damselfishes from the Gulf of California, Mexico, use contrasting behaviors when feeding on benthic algal communities. The small (±70 g) Cortez damselfish, Eupomacentrus rectifraenum (Gill, 1862), feeds selectively from a multi-species algal mat, eats fleshy red and green algae and ignores brown and calcareous algae. The giant blue damselfish, Microspathodon dorsalis (Gill, 1862), is a large (±450 g), lethargic, nonselective feeder which grazes on a near monoculture of a fleshy red alga, Polysiphonia sp. Feeding activity for both species is low in the morning peaks during late afternoon, and drops sharply as night approaches. Based on feeding rates, gut-filling times, and weights of gut contents, Cortez damselfish process six to eight full guts of food and giant blue damselfish three full guts of food per day. The algal mat exhibits high standing crops (291–618 g dry wt · m^?2) and low productivity, but the preferred food of the Cortez damselfish (Ulva) appears to colonize the mat frequently and grow rapidly. The Polysiphonia dominated community on giant blue damselfish territories exhibits low standing crops (23 g · m^?2) and high productivity (34–47 times that of the mat per gram algae). Even though the feeding behaviors and resources used by the two damselfishes differ, both species eat similar food (delicate red and green fleshy algae, and depend on rapid colonization and/or high productivity to maintain their primary foods in the grazed algal community.     

Role of algae in the diet of Chironomus plumosus F. semireductus from the Bay of Quinte,Lake Ontario

The importance of algae and different algal species to the chironomid diet was investigated through examination of the guts of chironomids taken from 5 locations in Big Bay (Bay of Quinte, Lake Ontario) at 6 times during the ice-free period. A comparison of the density and condition of algal cells at the two ends of the gut provided information on the digestibility of each algal species and the algal biomass assimilated by the chironomids. Diatoms and two species of green algae were assimilated over much of the summer, but the blue green algae were digested only late in the season when their populations were aged and/or dying. In terms of energy contribution, diatoms, especially Stephanodiscus spp. and Melosira spp., were most important in May (99% of all algal biomass assimilated), August (98%), and Octobr (92%), while the blue green species, Microcystis aeruginosa, was predominant in September (76%). Only a few small greens were assimilated in June and July. The contribution of algae as a food source to chironomid energetics was small, and reached a maximum in August and September (15%–34%). It is postulated that bacteria are a more important food source.     

Testing for the induction of anti-herbivory defences in four Portuguese macroalgae by direct and water-borne cues of grazing amphipods

Herbivory is a key factor in regulating plant biomass, thereby driving ecosystem performance. Algae have developed multiple adaptations to cope with grazers, including morphological and chemical defences. In a series of experiments we investigated whether several species of macroalgae possess anti-herbivore defences and whether these could be regulated to demand, i.e. grazing events. The potential of direct grazing on defence induction was assessed for two brown (Dictyopteris membranacea, Fucus vesiculosus) and two red seaweeds (Gelidium sesquipedale, Sphaerococcus coronopifolius) from São Rafael and Ria Formosa, Portugal. Bioassays conducted with live algal pieces and agar-based food containing lipophilic algal extracts were used to detect changes in palatability after exposure to amphipod attacks (=treatment phase). Fucus vesiculosus was the only species significantly reducing palatability in response to direct amphipod-attacks. This pattern was observed in live F. vesiculosus pieces and agar-based food containing a lipophilic extract, suggesting that lipophilic compounds produced during the treatment phase were responsible for the repulsion of grazers. Water-borne cues of grazed F. vesiculosus as well as non-grazing amphipods also reduced palatability of neighbouring conspecifics. However, this effect was only observed in live tissues of F. vesiculosus. This study is the first to show that amphipods, like isopods, are capable to induce anti-herbivory defences in F. vesiculosus and that a seasonally variable effectiveness of chemical defences might serve as a dynamic control in alga–herbivore interactions.     

Accounting for Algae

Interest and research in the use of algae for energy is growing but an analysis of the different methods for the accounting for the carbon dioxide (CO ₂) emissions that result, is lacking. In this article, four accounting systems are evaluated for their completeness, simplicity, sectoral accuracy, and scale‐independence. Two options under the Kyoto Protocol (KP), a value‐chain (end‐user responsibility) approach, and Point of Uptake and Release (POUR) are evaluated. Algal material is used in biofuels, animal feeds, human foods, and food supplements, and a range of products such as paints, cosmetics, and plastics. There are also proposals for using algae as a soil amendment. This variety of uses for algal material together with the fact that it will probably contain carbon of fossil origin presents accounting challenges and reveals inconsistencies that have lain in the KPs treatment of biomass emissions. Furthermore, a key conclusion of the article is that neither proposed KP accounting approach for algae leads to correct accounting of emissions for all uses. Both value chain and POUR approaches more correctly and consistently account for algal emissions across uses. POUR offers the potential to provide comprehensive, consistent emission accounting across all uses of biomass, which represents a major step forward in accounting for CO ₂ emissions due to use of biomass.     

Evaluation of The Safety and Efficacy of Newly Developed Domestic Allergenic Extracts for Skin Prick Testing

Background:Allergic disorders are common health problems worldwide with significant socio-economic impacts. The best diagnostic method using allergenic extract is the skin prick test. Regarding the effects of geo-climatic factors and allergenic extract source material quality, the aim of study was to determine the safety and efficacy of some in-house-developed allergenic extracts.Methods:Forty-five different allergenic extracts, including common regional pollen, foods, and dog and cat hair, as well as positive and negative extracts, were prepared from domestic sources using optimum extraction methods. All extracts passed stability and sterility testing, and sterile final products containing 50% glycerin in 10 and 20 w/v concentrations were used. Skin prick testing was performed on volunteers and immediate or late side effects were recorded. Results:In total, 56 students (mean age: 21.2±2.3y, M/F ratio: 1.07) participated in this study. For inhalant allergens, all extracts except dog hair extract caused positive responses. Salsola kali (Russian thistle) and Fraxinus velutina (ash tree) were the most common grass and tree pollen extracts, respectively. Of 18 different food extracts, five, including egg white, tomato, fig, melon, and green pepper caused skin reactivity in only one person. No participant reported any immediate or late side effects, including large local reaction or systemic response.Conclusion:The result of the current study confirmed the safety of all our in-house-developed allergenic extracts. Regarding efficacy, almost all inhalant and five food allergens caused positive skin responses.Key Words: Allergenic extract, In-house extract, Skin prick test     

Marine macroalgae as foods for fishes: an evaluation of potential food quality

Synopsis A revitalized view of feeding by herbivorous marine fishes is sought through two questions. First, What characteristics of major taxa of algae identify them as predictably high or low quality foods? Second, are marine algae valuable foods for fishes which do not mechanically disrupt cell walls and do not harbor specialized enzymes or microbes capable of lysing cell walls? Energy, ash and nutrient content of 16 species of marine algae were employed to assess food quality of fleshy red, green, brown and calcareous red algae. On the basis of ash, calories, total protein and total lipid content, fleshy algae should be superior to calcareous algae as foods for fishes; in addition, green algae should be superior to brown algae and brown algae superior to red algae. When the probable digestibility of storage and extracellular carbohydrates is considered, green and red algae are predicted superior to brown algae as food. Two species of damselfishes (Pomacentridae) from the Gulf of California,Eupomacentrus rectifraenum andMicrospathodon dorsalis, eat red and green algae and ignore brown and calcareous algae. They feed, therefore, in a fashion consistent with predictions based only on algal chemistry. These fishes absorb at least 20–24% of the biomass, 57–67% of the protein, 46–56% of the lipid and 37–44% of the carbohydrate contained in algae eaten in the wild. Since these damselfishes do not masticate their food, it appears that herbivorous fishes can digest major fractions of algal nutrients without mechanical destruction of algal cells.     

普生轮藻浸提液对两种淡水藻类的化感抑制作用及其数学模型

利用大型水生植物的化感作用抑制水华藻类是水域生态学研究的热点课题之一。探讨了不同浓度普生轮藻浸提液对产毒铜绿微囊藻和斜生栅藻(单纯以及混合藻类)的抑制作用,并根据实验过程中得到的数据和数据特征,在传统的Logistic模型和Lotka-Volterra模型基础上,通过微元法建立了普生轮藻浸提液对单纯产毒铜绿微囊藻、单纯斜生栅藻抑制的数学模型以及两藻混合时抑制的数学模型。结果表明,(1)普生轮藻浸提液无论对单独的毒性铜绿微囊藻或斜生栅藻还是共生状态的毒性铜绿微囊藻和斜生栅藻均有很强抑制作用,且对毒性铜绿微囊藻的抑制作用要显著高于对斜生栅藻;(2)所建立的抑藻模型可有效表征和预测在一定范围内的产毒铜绿微囊藻、斜生栅藻及其混合藻在普生轮藻浸提液胁迫下藻密度随时间变化的规律;通过这些模型可方便地计算出实验期间任何时间节点上普生轮藻浸提液的半抑制浓度(EC50)、最小有效浓度(MIC)等指标的预测值、混合藻在小生境中相对稳定时的预测值等等。该研究可为实际抑藻的方案制定和实施提供有价值的数据支撑和参考,具有一定的理论与应用意义。     

Effect of phlorotannin-rich extracts of Ascophyllum nodosum and Himanthalia elongata (Phaeophyceae) on cellular oxidative markers in human HepG2 cells

Phlorotannins have received much attention due to their ecophysiological importance and potential applications in the biotechnology and food industries. Antioxidant activity studies in seaweeds have mainly focused on in vitro assays; however, there is a paucity of data regarding the effect of brown algal phlorotannins on living cultured cells. The aim of the present study was to investigate both direct and protective effects of phlorotannin-rich extracts on cell viability and the cellular oxidative status of cultured liver cells HepG2 against oxidative stress induced by tert-butyl hydroperoxide (t-BOOH). Extracts of the Phaeophyceae Ascophyllum nodosum (Fucaceae) and Himanthalia elongata (Himanthaliaceae) were submitted to gastrointestinal digestion prior to incubation for 20 h in a HepG2 culture at physiological concentrations (0.5–50 μg mL^?1). Various markers of cellular oxidative stress were then assessed, such as the generation of reactive oxygen species (ROS), antioxidant defences (concentration of reduced glutathione and activities of glutathione peroxidase, reductase and glutathione-S-transferase) and the levels of malondialdehyde as a marker for lipid peroxidation. The direct effect on cellular markers was assessed immediately after the incubation period, whereas for the protective effect, the incubation period was followed by a 3-h treatment with t-BOOH. The results indicated no effect on cell viability, and both extracts showed reduced levels of ROS and increased antioxidant defences in the direct treatment. Moreover, the extracts showed a significant protective effect against chemically induced oxidative stress in HepG2 cells by reducing ROS generation and enhancing antioxidant defences, hence supporting the utility of including brown algal extracts in functional food products.     

Strategies to enhance production of microalgal biomass and lipids for biofuel feedstock

ABSTRACT

Microalgae have enormous potential as feedstock for biofuel production compared with other sources, due to their high areal productivity, relatively low environmental impact, and low impact on food security. However, high production costs are the major limitation for commercialization of algal biofuels. Strategies to maximize biomass and lipid production are crucial for improving the economics of using microalgae for biofuels. Selection of suitable algal strains, preferably from indigenous habitats, and further improvement of those ‘platform strains’ using mutagenesis and genetic engineering approaches are desirable. Conventional approaches to improve biomass and lipid productivity of microalgae mainly involve manipulation of nutritional (e.g. nitrogen and phosphorus) and environmental (e.g. temperature, light and salinity) factors. Approaches such as the addition of phytohormones, genetic and metabolic engineering, and co-cultivation of microalgae with yeasts and bacteria are more recent strategies to enhance biomass and lipid productivity of microalgae. Improvement in culture systems and the use of a hybrid system (i.e. a combination of open ponds and photobioreactors) is another strategy to optimize algal biomass and lipid production. In addition, the use of low-cost substrates such as agri-industrial wastewater for the cultivation of microalgae will be a smart strategy to reduce production costs. Such systems not only generate high algal biomass and lipid productivity, but are also useful for bioremediation of wastewater and bioremoval of waste CO₂. The aim of this review is to highlight the advances in the use of various strategies to enhance production of algal biomass and lipids for biofuel feedstock.     

Effect of food preservation on the grazing behavior and on the gut flora of the harpacticoid copepod Paramphiascella fulvofasciata

Harpacticoids owe their ‘reputation’ as primary consumers in aquatic food webs to their substantial grazing on diatoms, thus assuring an efficient energy flow to higher trophic levels. Due to the complex feeding behavior of harpacticoids, the nature and dynamics of diatom-harpacticoid trophic interactions remain poorly understood. In addition, there is a growing interest from aquaculture industry in mass-culturing harpacticoids with algal foods but the labor costs of maintaining algal stock cultures are high. This study focuses on the palatability of preserved diatoms for copepods and considers the possible role of bacterially mediated effects on diatom food uptake.The grazing of Paramphiascella fulvofasciata on a preserved freeze-dried diatom diet was tested and compared to the grazing on fresh cells. P. fulvofasciata assimilated the preserved diet, but assimilation of fresh cells was higher. When both cell types were mixed, no selective feeding was observed. Community fingerprinting of the bacteria associated with diatoms and fecal pellets suggests that the copepod gut flora was modified depending on the food source. Furthermore, the results suggest that the egestion of gut bacteria enriches the microenvironment and this can have an additional influence on the feeding behavior of the copepod.Experimental research using preserved foods must take into account that copepod grazing assimilations of fresh foods are likely to be significantly higher. Yet, the stated high assimilation of the mixed diet, encourages further exploration of the application of preserved ‘balanced’ foods for harpacticoid mass-culturing.     

Responses of algae, bacteria, Daphnia and natural parasite fauna of Daphnia to nutrient enrichment in mesocosms

Understanding responses of parasites to changes in nutrient regimes is necessary for prediction of their role in aquatic ecosystems under global change in nutrient loading. We studied the response of the natural parasite fauna of Daphnia longispina to nutrient enrichment in mesocosms in a small humic lake. We measured the concentrations of inorganic phosphorus and nitrogen in the water, total nutrients in the seston, algal and bacterial biomass, Daphnia population dynamics, Daphnia stoichiometry, Daphnia stable isotope values and the presence and abundance of parasites in treated mesocosms as compared to three control ones. Incorporation of the nutrient enrichment in the food web was seen as increased nutrient concentrations in the epilimnion and as a decrease in carbon:nutrient ratios and δ¹⁵N values in Daphnia. Nutrient enrichment did not significantly influence algal, bacterial or Daphnia biomass. One of the four parasite species observed, unidentified small gut parasite, had a higher prevalence (percentage of Daphnia infected) in treated mesocosms, but its intensity (number of parasites per infected host) remained the same among treatments. Our results suggest that the effect of nutrient enrichment on host–parasite dynamics is dependent on complex interactions within food webs and on the epidemiological traits of parasites.     

Long-term trends in food habits of Asiatic black bears in the Misaka Mountains on the Pacific coast of central Japan

I did the food habits of the Asiatic black bear Ursus thibetanus from 1013 fecal samples collected between 1999 and 2005 in the Misaka Mountains on the Pacific coast of central Japan. The food habits of the bears showed clear seasonal changes, and I classified the food resources of the bears into three types. Staple foods were green vegetation in spring, soft mast (Prunus spp.) and insects in summer, and hard mast (Quercus spp.) in autumn. Alternative foods were green vegetation and other soft mast (Rubus spp.) in summer and Japanese chestnuts Castanea crenata and vine fruits in autumn. Foods of opportunity were hard mast (Quercus spp.) that had been shed in the previous autumn and were found in spring and other fruits in autumn. Seasonal food habits showed yearly variations: bears used alternative foods and foods of opportunity in response to the yearly variation in staple food amount, but the magnitude of variability of food habits differed among seasons, with large variability in autumn and small variability in summer and spring. The primary influence on the yearly variation in food habit is presumably the fluctuation in fruit production among years. Summer is probably the most difficult season in terms of the bear's food supply, because the number of fruiting species is limited and staple foods such as new green vegetation and fruits are less available. Long-term studies of the availability of the main food items and food habits of bears will be critical for further understanding these animals’ feeding ecology and for determining the factors that influence their behavior.     

Position of horseshoe crabs in estuarine food webs: N and C stable isotopic study of foraging ranges and diet composition

To discern the position of horseshoe crabs as a potentially important predator in estuarine food webs, we determined where they foraged and what they ate. We used N and C stable isotopes to link adult horseshoe crabs to their oraging locations and potential food sources in Pleasant Bay, Cape Cod. The δ¹⁵N in tissues of horseshoe crabs and their potential foods suggest crabs were loyal to local foraging sites and did not forage substantially in subestuaries receiving >110 kg N ha⁻¹ year⁻¹. Among locations where crabs foraged, δ¹³C values in potential foods showed that food webs in subestuaries subject to higher N loads were supported by algal producers, while food webs in subestuaries with lower N loads were also supported by Spartina. δ¹³C values in horseshoe crab tissue did not change with load, suggesting they ate a mixed diet, regardless of N load. N and C isotopes in horseshoe crab feces were similar to signatures of estimated diet, suggesting low assimilation efficiency, perhaps due to ingestion of low quality organic matter. Although horseshoe crabs were relatively opportunistic in foraging habits, conservation or culture of horseshoe crabs may require habitats with higher water quality, ample particulate organic matter, and supporting a variety of prey.     

The impact of small chironomid grazers on epiphytic algal abundance and dispersion

• 1 A combination of field and laboratory experiments was used to assess the impact of chironomid grazers on taxonomic composition, abundance and dispersion of epiphytic algal assemblages.
• 2 In the laboratory, Psectrodadius sp. reduced the biovolume of algal species preferred as food and increased the degree of clumping of non-preferred species. Thienemanniella cf. fusca had both positive and negative effects (depending on the algal species) on the biovolumes of algal species preferred as food and increased the degree of clumping of non-preferred species.
• 3 In field exclosures, no effect of removal of chironomid larvae from the grazer assemblage could be detected in autumn or winter experiments. A third, longer removal experiment, conducted in summer, resulted in increased biovolumes of edible Cosmarium spp. and Aphanocapsa spp., preferred foods of chironomid larvae. Biovolumes of Lyngbya sp., Eulbochaete spp. and Oedogortium spp., filamentous taxa used extensively in larval case construction, also increased. Chironomid larvae had no effect on total algal biovolume or biovolume of large unicellular algae.
• 4 Chironomid larvae can influence epiphytic algal assemblages through selective grazing by reducing the biovolumes of preferred foods and through case-building activity by reducing the biovolumes of construction materials.