José A. Zertuche-González

Integrating seaweeds into marine aquaculture systems: a key toward sustainability

The rapid development of intensive fed aquaculture (e.g. finfish and shrimp) throughout the world is associated with concerns about the environmental impacts of such often monospecific practices, especially where activities are highly geographically concentrated or located in suboptimal sites whose assimilative capacity is poorly understood and, consequently, prone to being exceeded. One of the main environmental issues is the direct discharge of significant nutrient loads into coastal waters from open‐water systems and with the effluents from land‐based systems. In its search for best management practices, the aquaculture industry should develop innovative and responsible practices that optimize its efficiency and create diversification, while ensuring the remediation of the consequences of its activities to maintain the health of coastal waters. To avoid pronounced shifts in coastal processes, conversion, not dilution, is a common‐sense solution, used for centuries in Asian countries. By integrating fed aquaculture (finfish, shrimp) with inorganic and organic extractive aquaculture (seaweed and shellfish), the wastes of one resource user become a resource (fertilizer or food) for the others. Such a balanced ecosystem approach provides nutrient bioremediation capability, mutual benefits to the cocultured organisms, economic diversification by producing other value‐added marine crops, and increased profitability per cultivation unit for the aquaculture industry. Moreover, as guidelines and regulations on aquaculture effluents are forthcoming in several countries, using appropriately selected seaweeds as renewable biological nutrient scrubbers represents a cost‐effective means for reaching compliance by reducing the internalization of the total environmental costs. By adopting integrated polytrophic practices, the aquaculture industry should find increasing environmental, economic, and social acceptability and become a full and sustainable partner within the development of integrated coastal management frameworks.

Seaweeds: an opportunity for wealth and sustainable livelihood for coastal communities

The European, Canadian, and Latin American seaweed industries rely on the sustainable harvesting of natural resources. As several countries wish to increase their activity, the harvest should be managed according to integrated and participatory governance regimes to ensure production within a long-term perspective. Development of regulations and directives enabling the sustainable exploitation of natural resources must therefore be brought to the national and international political agenda in order to ensure environmental, social, and economic values in the coastal areas around the world. In Europe, Portugal requires an appraisal of seaweed management plans while Norway and Canada have developed and implemented coastal management plans including well-established and sustainable exploitation of their natural seaweed resources. Whereas, in Latin America, different scenarios of seaweed exploitation can be observed; each country is however in need of long-term and ecosystem-based management plans to ensure that exploitation is sustainable. These plans are required particularly in Peru and Brazil, while Chile has succeeded in establishing a sustainable seaweed-harvesting plan for most of the economically important seaweeds. Furthermore, in both Europe and Latin America, seaweed aquaculture is at its infancy and development will have to overcome numerous challenges at different levels (i.e., technology, biology, policy). Thus, there is a need for regulations and establishment of “best practices” for seaweed harvesting, management, and cultivation. Trained human resources will also be required to provide information and education to the communities involved, to enable seaweed utilization to become a profitable business and provide better income opportunities to coastal communities.

Distribution and Quantification of Sargassum Beds along the West Coast of the Gulf of California, Mexico

The biomass of the genus Sargassum, in twenty two beds along the NW coast of the Gulf of California, was quantified in spring 1995 and 1996. In Baja California, 18 beds consist almost exclusively of Sargassum johnstonü Setch. et Gardn. and one of Sargassum sinicola Setch. et Gardn. In Baja California Sur, three beds of Sargassum were detected, mostly made up of Sargassum herporhizum Setch. et Gardn., Sargassum lapazeanum Setch. et Gardn. and Sargassum sinicola Setch. et Gardn. The majority of the plants studied were reproductive. Exceptionally large S. johnstonü plants (> 10m) were found in the northern region. Previous records for this species in the Gulf of California were for less than two meters. The beds cover a total area of 1113 hectares, with an average biomass of 16.4 kg m~ wet weight in Baja California and 5.0 kg m~ wet weight in Baja California Sur. The total biomass was 154000 ± 16000 wet tons or 31 000 ± 3200 dry tons. The biomass determined was the highest ever reported for any species from west coast of the Gulf of California.

Open water Chondrus crispus stackhouse cultivation.

Selected strains of Chondrus crispus were acclimated to relativelywarm Pacific waters off the Baja California peninsula, Mexico, and werecultured in semi-exposed oceanic conditions. Specific techniques weredeveloped for culturing this species in semi-exposed oceanic environment,in an effort to establish the basis for its commercial farming. This is the firsttime that Chondrus crispus has been cultured in the ocean and outsideits natural Atlantic environment. The information generated in this studyis being used to feed an economic model to test the feasibility of thecommercial culturing of Chondrus crispus.

Gracilariopsis lemaneiformis beds along the west coast of the Gulf of California, Mexico

The seasonal variation of the biomass of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik was measured for 18 months in Bahía de las Ánimas. Maximum biomass per unit area (11.1 kg wet wt m−2) occurred in the spring of 1995 and most of the biomass was lost by summer. Agar gel strength and yield were 891 g cm−2 and 14%, respectively for spring samples. Biomass per unit area was also evaluated during spring from all the beds of G. lemaneiformis in 850 km of the west coast of the Gulf of California. The total biomass estimated in 1995 was 5751 ± 404 dry t. The total biomass for spring of 1996 was about 30% less (4060 ± 246 dry t). Commercial exploitation of G. lemaneiformis started in the west coast of the Gulf of California in 1995.

Biomass and potential commercial utilization of Ulva lactuca (Chlorophyta, Ulvaceae) beds along the north-west coast of the Gulf of California

Abstract The biomass of Ulva lactuca beds on the west coast of the Gulf of California was evaluated in 1995, 1996, 1998 and 2000. The total biomass was estimated at four localities, for a total of 12 km of the coastline and a total Ulva bed area of 2.2 km2, and amounted to > 350 tonnes dry weight per year. The pristine conditions of the area make this biomass particularly suitable for commercial utilization as food, food ingredients and fodder. Lower biomass in 1998 apparently reflects an ENSO event.

Ecological effects of seaweed harvesting in the Gulf of California and Pacific Ocean off Baja California and California

The ecological effects of harvesting were investigated for two species, the giant kelp Macrocystis pyrifera and Eucheuma uncinatum, by using harvest records and aerial surveys that show yield changes and by using studies of recruitment, survivorship and community interactions. There were no ecological effects found for M. pyrifera harvested with contemporary methods, and there are no recommendations for changing current management practices for this species. It is recommended that E. uncinatum, which on occasion produces commercially significant standing crops, not be harvested unless special precautions are taken to leave some plants for regeneration of the harvested populations.

Giant kelp (Macrocystis pyrifera) survival in deep water (25-40 m) during El Nino of 1997-1998 in Baja California, Mexico

Abstract During the 1997–1998 El Niño, we examined seasonally a giant kelp population in deep water (25–40 m) off the coast of Northern Baja California. Though most populations in the region completely disappeared, large fertile adults survived the entire warming event at depth. At 25 m, there was no significant change in density or number of fronds per individual during the warming period from spring 1997 to spring 1998, though the surface canopy sloughed off (died) down to 15 m depth. By summer 1998, recruitment occurred at all depths at the site. Adult survival at depth was most likely important in post-disturbance recovery in surrounding populations by occupying substratum, providing vegetative growth, and producing spores. Survival in deep water during this extreme El Niño may have been due to local hydrography, such as internal waves bringing cool nitrate-rich water into the deeper regions of the shelf from below the thermocline, providing a refugium against the warm temperatures, low nutrients, and heavy wave action associated with warming events. Deep-water populations may regularly survive El Niño warming in this region due to internal wave activity, and go undetected due to the depth at which they occur and the sloughing of the shallow (<15 m) biomass.

Brown algae (Phaeophyta) from Bahía de los Angeles, Gulf of California, México

Seven sites in Bahía de los Angeles, northern Gulf of California, were sampled seasonally over a three-year period. Five species of brown algae previously not recorded from this bay were identified: Ralfsia pacifica, Sporochnus balleanus, Hydroclathrus clathratus, Colpomenia sinuosa and Padina mexicana. Of these, H. clathratus also provided a new record for the northern Gulf of California. One species previously recorded from the bay, Dictyopteris undulata, was not observed. On a seasonal basis, temperature and biodiversity showed an inverse relationship: highest species numbers occurred in spring, when temperatures were lowest, and lowest species numbers occurred in autumn when temperatures were highest. Most species of brown algae in Baífa de los Angeles are annuals.

Influence of alkali treatment on agar from Gracilariopsis longissima and Gracilaria vermiculophylla from the Gulf of California, Mexico

The effect of alkali treatment on agar yield, sulfate content, and 3,6 anhydrogalactose content from two agarophyte species (Gracilariopsis longissima and Gracilaria vermiculophylla) was analyzed. In addition, gel strength was measured in each agar extract as well as gelling and melting temperatures. Agar was extracted after pretreatment with different concentrations of NaOH (3%, 5%, 7%, and 9%). Pretreatment with alkali significantly reduced agar yield from G. longissima from 13.2% in nontreated agar (native agar) to 5.4% in 5% NaOH, whereas in G. vermiculophylla it diminished from 25.2% to 9.6% in 9% NaOH treatment. Statistically significant differences were observed for native and all alkali treatments in G. longissima, whereas in G. vermiculophylla significant differences were only found among native and high alkali treatments (7% and 9% NaOH, P < 0.05). Sulfate content from G. longissima diminished gradually with increasing alkali concentration, from high (3.9%) in native agar to low (3.1%) in 7% alkali treatment, and was negatively correlated with gel strength (r = –0.92). Sulfate content in G. vermiculophylla native agar was twice as high as that found in G. longissima (7.8%) and did not show statistically significant differences with low alkali treatments, but it did with high NaOH treatments. Higher contents of 3,6 anhydrogalactose were found with 9% NaOH treatment in G. longissima (40.9%) and G. vermiculophylla (43%), and they were significantly correlated with gel strength (r = 0.89 and r = 0.91, respectively).