Rhodora V. Azanza

Advances in cultivation technology of commercial eucheumatoid species: a review with suggestions for future research

An “advance” is defined as any technology that leads to an increase in production of Kappaphycus alvarezii (Doty) Doty, K. striatum Schmitz and Eucheuma denticulatum (Burman) Collins et Harvey (commercial eucheumatoid species) per unit time, effort, area and cost in more than one cultivation area. The present review has shown that no true advances have taken place in commercial eucheumatoid farming in over a decade. These species have remained the primary source of carrageenan through expansion of cultivation area and increase in the number of farmers since farmer productivity has not increased through time. Priority should be given to researches that could replace “tie–tie system” currently being used in the vegetative propagation of the crops and the possible use of spores/sporelings in cultivation as in other economic seaweeds. Multifactorial experiments considering nutrients, salinity and light especially, need to be done to meet seasonality problems in growth/production of the crops. Understanding and developing the capability to mitigate or eliminate pests, herbivores and diseases need to be addressed more closely. Strains should be developed through a continuous selection of wild varieties, breeding programs and genetic manipulation or transgenic production/development. Increasing the quality of extract through superior post-harvest handling and strain improvement should be achieved. Practical and effective quarantine procedures should be explored, publicized and utilized for introduction of crops to new areas.

Occurrences of harmful algal blooms (HABs) associated with ocean environments in the South China Sea

Harmful algal blooms (HABs) occur frequently in the South China Sea (SCS), causing enormous economic losses in aquaculture. We analyzed historical HAB records during the period from 1980 to 2003 in SCS. We found that HABs-affected areas have expanded and the frequency of HABs varied during this period. The seasonal and annual variations, as well as causative algal species of HABs are different among the four regions. Areas with frequent HABs include the Pearl River Estuary (China), the Manila Bay (the Philippines), the Masinloc Bay (the Philippines), and the western coast of Sabah (Malaysia). HABs occurred frequently during March–May in the northern region of SCS, May–July in the eastern region, July in the western region, and year-round in the southern region. Among the species that cause HABs, Noctiluca scintillans dominated in the northern region, and Pyrodinium bahamense in the southern and eastern regions. Causative species also varied in different years for the entire SCS. Both P. bahamense and N. scintillans were the dominant species during 1980–2003. Some species not previously recorded formed blooms during 1991–2003, including Phaeocystis globosa, Scrippsiella trochoidea, Heterosigma akashiwo, and Mesodinium rubrum. Variations in HABs are related to various regional conditions, such as a reversed monsoon wind in the entire SCS, river discharges in the northern area, upwelling in Vietnam coastal waters during southwest winds and near Malaysia coastal waters during northeast winds, and eutrophication from coastal aquaculture in the Pearl River estuary, Manila Bay, and Masinloc Bay.

Eutrophic waters, algal bloom and fish kill in fish farming areas in Bolinao, Pangasinan, Philippines

The coastal waters of Bolinao, Pangasinan, Philippines experienced environmental changes over a 10-year period (1995-2005), the most significant effect of which was the major fish kill event in 2002 that coincided with the first reported Philippine bloom of a dinoflagellate Prorocentrum minimum. Days before the bloom, dissolved oxygen was < 2.0 mg/l in the waters that were stratified. These conditions may be linked to the uncontrolled proliferation of fish pens and cages to more than double the allowable limit of 544 units for Bolinao waters. Mariculture activities release organic matter from unconsumed feed and fecal material that accumulate in the water and sediments. In over 10 years, water quality conditions have become eutrophic with ammonia increasing by 56%, nitrite by 35%, nitrate by 90%, and phosphate by 67%. The addition of more fish pens and cages placed additional stress to this poorly flushed, shallow area that affected water quality due to changes in the water residence time.

Ocean urea fertilization for carbon credits poses high ecological risks

The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.

Horizontal dinoflagellate cyst distribution, sediment characteristics and benthic flux in Manila Bay, Philippines

The lateral variation of sediment properties and associated cyst content of sediment in Manila Bay were determined and their possible role/s in the occurrences of Pyrodinium bahamense Plate var. compressum (Bohm) Steidinger, Tester et Taylor toxic blooms were assessed. Manila Bays surface sediment was determined to be silt dominated. Clay generally increased towards the coast, probably as a result of flocculation and rapid deposition upon entry of sediments from the rivers. High sand content characterized the southeastern part of the bay attributed to the greater sand inputs and relatively strong currents in this area. Bulk densities were lower in the eastern side of the bay from dilution by high organic load from sewage and urban areas. Benthic flux calculations, particularly NH3, suggest more than 50% nutrient contribution comes from sediments.

Thalassic biogas production from sea wrack biomass using different microbial seeds: cow manure, marine sediment and sea wrack-associated microflora.

Sea wrack (dislodged sea grasses and seaweeds) was used in biogas production. Fresh water scarcity in island communities where sea wrack could accumulate led to seawater utilization as liquid substrate. Three microbial seeds cow manure (CM), marine sediment (MS), and sea wrack-associated microflora (SWA) were explored for biogas production. The average biogas produced were 2172±156 mL (MS), 1223±308 mL (SWA) and 551±126 mL (CM). Though methane potential (396.9 mL(CH4) g(-1) volatile solid) computed from sea wrack proximate values was comparable to other feedstocks, highest methane yield was low (MS=94.33 mL(CH4) g(-1) VS). Among the microbial seeds, MS proved the best microbial source in utilizing sea wrack biomass and seawater. However, salinity (MS=42‰) observed exceeded average seawater salinity (34‰). Hence, methanogenic activity could have been inhibited. This is the first report on sea wrack biomass utilization for thalassic biogas production.

Manila Bay: Environmental Challenges and Opportunities

Manila Bay has a wide range of environmental problems that need to be addressed — from land-based and sea-based sources of pollution to harmful algal blooms, subsidence and groundwater extraction, overexploitation of fishery resources, and habitat conversion and degradation. However, there are reasons to be optimistic. There is greater accountability expected of public officials vis-a-vis environmental laws, significant and increasing infrastructure investments to treat and reduce domestic sewage discharges into the bay, the implementation of the Manila Bay Environmental Management Project, and the adoption the concept and practice of ICM by local government units and communities around Manila Bay.

Decimal reduction times of Pyrodinium bahamense var. compressum and Escherichia coli in chlorine-and ultraviolet-treated seawater

Aims: Decimal reduction times (D‐values) of the vegetative cells of Pyrodinium bahamense var. compressum and Escherichia coli in ultraviolet‐ and chlorine‐treated seawater were established.

Development, morphological characteristics and viability of temporary cysts of Pyrodinium bahamense var. compressum (Dinophyceae) in vitro

Pellicle or temporary cysts of Pyrodinium bahamense var. compressum (Böhm) Steidinger, Tester & F.J.R. Taylor and their role in bloom dynamics have not yet been adequately characterized and understood. We investigated the role of temperature- and nutrient-mediated stress as factors that could induce pellicle formation in batch cultures. Cellular features and their implications for temporary cyst viability were examined using confocal laser scanning microscopy (CLSM). Our data suggest that temperature change is one of the key factors influencing pellicle formation, preserving viability at low temperature (i.e. 13°C). Hypnocysts (resting cysts) were not observed. During pellicle formation, motile cells generally undergo ecdysis, extrusion of cytoplasmic materials and bacteria, compaction of the nucleus and non-motility. The outermost covering of the temporary cysts shows red autofluorescence and it contains lower concentrations of chlorophyll (chl) a and no detectable chl c. The nuclear region is surrounded by transitional red bodies and other unidentified cellular structures. Temporary cysts can immediately revert back to the motile state upon exposure to optimum conditions. This is accompanied by the expansion of the nuclear region, regeneration of the chloroplasts and enlargement of the cell. Developmental changes during reversal of temporary cysts to motile forms were also observed to cause breaks in the cell covering that could serve as sites for bacterial entry. Though observed in vitro, such behaviour may also be occurring in nature especially as a response to drastic short-lived environmental changes. This is the first detailed report on the characteristics of temporary cysts of P. bahamense var. compressum.

Overview of Harmful Algal Blooms in Asia

Harmful algal blooms (HABs), contributing to both fisheries effects due to high-biomass algal blooms and shellfish or fish poisoning due to toxic algae, have long been reported in coastal waters of the Asian region, especially in East and Southeast Asia. HAB-related issues have continuously been of both social and economic concern. Although there have been continuous efforts to investigate various aspects of harmful algae, new records of fish mass mortality due to species previously undetected at particular sites have continued to occur over the last decade. These cases suggest recent expansion or introduction of HAB species in the Asian region. In this chapter, progress in HAB research and recent issues regarding harmful algae are summarized together with descriptions of newly documented HAB species from Asia, to improve our understanding for future research and management of harmful algae in the Asian region.