The subtidal (10—15 m) assemblage in the relatively sheltered giant kelp forest at Stillwater Cove in Carmel Bay, California, consists of perennial species forming three major vertical layers: a Macrocystis pyrifera surface canopy, a dense subsurface canopy of another kelp, Pterygophora californica, and an understory of articulated and encrusting coralline algae. The kelp canopies alone or in combination can reduce bottom light to <30% (usually <1%) of surface influx. The effects of light reduction by these vegetation layers on algal recruitment and subsequent growth were determined by removing various combinations of canopies over a 2—yr period, and following subsequent changes relative to appropriate controls. Removing both M. pyrifera and P. californica canopies resulted in moderate recruitment of these species as well as of the annual brown alga Desmarestia ligulata var. ligulata. None of these algae recruited into control areas where one or both canopies were left intact. Highest brown and red algal recruitment occurred when both kelp canopies plus understory coralline branches were removed. Removal of the latter alone had no significant effect. The time of year when algal canopies were removed had little effect on the composition of subsequent algal colonization, as the recruitment of noncalcareous species occurred primarily during a short period in the spring. These results indicate that the relatively low levels of both physical and biological disturbance in Stillwater Cove allow the establishment of a few perennial algal species that inhibit their own recruitment, as well as invasion of other species, by shading. This contrasts with nearby kelp forests subjected to greater and more frequent disturbance, and characterized by a diverse assemblage of annual algal species.
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The aim of this study was to determine growth of (Gracilaria sp.) with different spreading time of thallus. The study was conducted from March to April 2017 in pond located in Domas Village, Serang Region, Banten Province. The experiment followed completely randomized design with the treatment of different time on spreading of seaweed thallus during the culture period (45 days). Treatments were without spreading (as control), spreading every 2 weeks, and spreading every 3 weeks. The observed variables were weight of seaweed thallus and several water quality parameters. Analysis of seaweed weight used ANOVA test and Tukey HSD test. The results showed that the spread seaweed thallus had a significant effect on weight gain in 0.05 level. It used 100 gram Gracilaria sp. as initial weight, treatment without spreading thallus produced 508 gram, spreading every 2 weeks produced 906 gram and spreading every 3 weeks produced 790 gram. Based on the weight gain of thallus, seaweed culture by spreading thallus every 3 weeks and 2 weeks seem to be able to increase productivity by 56% and 78%, respectively.
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A critical knowledge gap in the production of macroalgae for protein (animal feed) and lipid (bioenergy) is the ability of target species to grow in saline groundwater and thereby avoid competition with traditional crops. We assessed the effect of increased salinity (0.11 ppt–3 ppt) on the growth of 5 strains of the freshwater macroalgaOedogonium in laboratory cultures and subsequently on the productivity and biochemical composition in outdoor cultures under ambient conditions. Growth and biomass productivity decreased with increasing salinity in both experiments across all strains. However, in contrast to biomass productivity, protein content increased with increasing salinity and consequently, protein productivity (0.2–0.6 g DW m−2 day−1 ) did not decrease markedly as salinity increased. Salinity had inconsistent effects on the lipid content among the strains, with the content of 2 strains increasing 3 to 4-fold under the 3 ppt treatment compared to 0.11 ppt. However, lipid productivity decreased with increasing salinity for 4 of the 5 strains. Similarly, biomass energy values increased with increasing salinity across all strains while bioenergy productivity decreased. These findings demonstrate that Oedogonium grown in salinities of up to 3 ppt maintains its productivity as a source of protein, potentially for animal feed, but not for bioenergy.
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The low volume batches of highly-concentrated wastewater discharged from land-based marine recirculating aquaculture systems are ideally suited for treatment by halophyte planted constructed wetlands. To evaluate the role of plants and the effect of planting density on yield and performance in small-scale saline constructed wetlands (CWs), NH4 + + NO3 − + NO2 − = total dissolved inorganic nitrogen (TDIN) and dissolved inorganic phosphorus (DIP) were measured at regular intervals over 24 h periods. CWs were planted with the halophyte Salicornia europaea at high- and low-densities and were compared to the performance of unplanted controls. S. europaea plants were cropped regularly to assess potential commercial yield at the two densities. There was no significant effect of planting density on performance or crop yields and planted beds consistently outperformed the control beds removing 62.0 ± 34.6 mmol N m−2 d−1 (34–73% of influent TDIN) compared to 23.0 ± 26.8 mmol N m−2 d−1 (−1% to 41% of influent TDIN) by control beds. Results for DIP were less clear, significant removal occurred only once, with reduction of 18.3 ± 5.0 mmol P m−2 d−1 by planted beds and 18.1 ± 2.6 mmol P m−2 d−1 by the unplanted controls. The results demonstrate the effectiveness of halophyte-planted CW in treatment of marine aquaculture wastewater
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The low volume batches of highly-concentrated wastewater discharged from land-based marine recirculating aquaculture systems are ideally suited for treatment by halophyte planted constructed wetlands. To evaluate the role of plants and the effect of planting density on yield and performance in small-scale saline constructed wetlands (CWs), NH4 + + NO3 − + NO2 − = total dissolved inorganic nitrogen (TDIN) and dissolved inorganic phosphorus (DIP) were measured at regular intervals over 24 h periods. CWs were planted with the halophyte Salicornia europaea at high- and low-densities and were compared to the performance of unplanted controls. S. europaea plants were cropped regularly to assess potential commercial yield at the two densities. There was no significant effect of planting density on performance or crop yields and planted beds consistently outperformed the control beds removing 62.0 ± 34.6 mmol N m−2 d−1 (34–73% of influent TDIN) compared to 23.0 ± 26.8 mmol N m−2 d−1 (−1% to 41% of influent TDIN) by control beds. Results for DIP were less clear, significant removal occurred only once, with reduction of 18.3 ± 5.0 mmol P m−2 d−1 by planted beds and 18.1 ± 2.6 mmol P m−2 d−1 by the unplanted controls. The results demonstrate the effectiveness of halophyte-planted CW in treatment of marine aquaculture wastewater.
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Alaria esculenta populations from six different geographical locations on the Irish coast were examined for hybridization abilities, growth rates and genetic make-up with a view towards identifying a fast-growing strain suitable for aquaculture. Hybridization experiments under laboratory conditions with the three most geographically dispersed populations showed that all cross combinations were interfertile, although differences were found in survival, and in blade and hapteron morphology. A comparison of relative growth rates showed significant differences amongst the self-crosses and hybrids. The data of the hybridization experiments and growth rates under laboratory conditions show that the best population for the purpose of seaweed aquaculture are the Slea Head and Corbet Head self-crosses and their hybrids. Genetic fingerprinting of the internal transcribed spacer of the ribosomal DNA of five A. esculenta isolates from geographically separated populations in Ireland revealed no restriction length polymorphisms between the tested isolates and show that the A. esculenta populations around the Irish coast are clearly genetically homogenous in respect of the DNA region examined. The genetic analysis, interfertility of the populations, morphology and growth rates are discussed with a view to potential cultivation.
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As the world's population continues to grow, the way in which ocean industries interact with ecosystems will be key to supporting the longevity of food and social securities. Aquaculture is crucial to the future supply of seafood, but challenges associated with negative impacts could impede increased production, especially production that is efcient and safe for the environment. Using the typology established by The Economics of Ecosystems and Biodiversity Initiative, we describe how marine aquaculture could be influential in supporting ecosystem services beyond solely the production of goods, through provisioning services, regulating services, habitat or supporting services, and cultural services. The provision of these services will vary, depending on functional traits of culture species, biotic and abiotic characteristics of the surrounding environment, farm design, and operational standards. Increasing recognition, understanding, and accounting of ecosystem service provision by mariculture through innovative policies, financing, and certification schemes may incentivize active delivery of benefits and may enable efects at a greater scale.
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The farming of the red seaweed Kappaphycus alvarezii and related species as raw material for the hydrocolloid carrageenan rapidly spread from the Philippines in the late 1960s to Indonesia, Tanzania, and other tropical countries around the world. Although numerous studies have documented positive socioeconomic impacts for seaweed farming, factors such as diseases and distance to export markets have led to an uneven development of the industry. Using standard budgeting techniques, this study adapted production and market data from a FAO-led global review of seaweed farming to develop comparative enterprise budgets for eight farming systems in six countries (Indonesia, the Philippines, Tanzania, India, Solomon Islands, and Mexico). Although the basic technology package is the same across countries, the study revealed large differences in the economic performance of systems due to wide variations in farm prices and the scale of operations. Although seaweed farming is a suitable activity for small-scale producers, a minimum of 2,000 m of cultures lines are still necessary to ensure adequate economic returns. Greater farming plots may be needed if farm prices are well below the average farm prices paid in Indonesia and the Philippines. Policy recommendations are made to improve the economic potential of underperforming systems.
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The developmental regulation of mass cultures of “free-living” conchocelis (suspension cultures) of Porphyra leucosticta from Groton, CT (USA) has been studied in laboratory culture. The conchocelis filaments were vegetatively propagated and maintained in 15 l volumes at 15 °C, 40 μmol m−2 s −1 and 16 L:8 D. Conchosporangia formation was induced after four weeks by increasing the temperature up to 20 °C, maintaining a photon fluence rate of 40 μmol m−2 s −1 and decreasing the photoperiod to 8 L:16 D. Conchosporangial filaments were vegetatively propagated and maintained at these conditions for up to 24 weeks. Suspension cultures of conchosporangial filaments were induced to form and release conchospores (after 6–10 days) by decreasing the temperature to 15 °C, increasing the photon fluence rate to 60–100 μmol m−2 s −1 and lengthening the photoperiod to 12 L:12 D. Conchosporangial formation was found at all photoperiods, however, the ratio of conchosporangia to vegetative conchocelis increased as the photoperiod decreased. With higher photon fluence levels, conchospore release time was decreased, whereas at a temperature of 25 °C spore germination decreased. At their peak release, the quantity of conchospores increased from 7.14 to 18.3 million per gram of conchosporangia with a decrease in conchosporangia density from 1.582 to 1.125 mg ml−1 , respectively. On the average, one gram (dw) of free conchosporangia could release about 20 million conchospores at the peak period. These released conchospores were able to attach, germinate and develop into juvenile blades on the synthetic twine (3–5 mm in diameter) of standard nori nets (1.5 × 18 m). A total of 16 standard nets and eight small nets (2.0 × 2.5 m) were seeded by fixing the culture nets over a rotary wheel in a 2.5 × 2.5 × 0.5 m−3 tank containing the mature conchospore inoculum from the free-living conchosporangia cultures. Four seeded standard nori nets were transferred to the sea for nursery culture in Long Island Sound (USA). Conchosporeling densities from 255 to 325 conchosporelings cm−1 were produced. After 43 days of nursery culture, the blades grew to 1.49 ± 0.14 cm in length. Our results indicate that the use of “free-living” conchocelis suspension cultures may be an effective alternative technology in the commercial production of the Porphyra.
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This article outlines the development of commercial open- water algae farming in Zanzibar in a historic context, with special reference to actual events at the corporate level from the initiation of algae-farming to its present state. These events, which contain policies and intentions of implementation at the producer level, have an array of social implications for the algae-farming communities. The three aspects of these implications are delineated; (i) a changing mode of tenure rights of the farmed lagoon areas; (ii) a changing role for algae farmers, i.e. women; (iii) a qualitative change within the composition of indigenous productive activities, the latter being illustrated by a de- clining activity in agriculture. The article demonstrates the importance of the encounter between an indigenous liveli- hood system and infused incentives pertaining to divergent rationales of livelihood in socioeconomic development processes.
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