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The Fancy Food Show in San Francisco is the West Coast’s largest food and beverage trade show. This is where the next big thing shows up first. In recent years, it was kale, kombucha, and almost anything that tastes like bacon. This year, it’s seaweed.

Ocean acidification (OA) is likely to differentially affect the biology and physiology of calcifying and noncalcifying taxa, thereby potentially altering key ecological interactions (e.g., facilitation, competition, predation) in ways that are difficult to predict from single-species experiments. We used a two-factor experimental design to investigate how multispecies benthic assemblages in southern California kelp forests respond to OA and grazing by the purple sea urchin, Strongylocentrotus purpuratus. Settlement tiles accrued natural mixed assemblages of algae and invertebrates in a kelp forest off San Diego, CA for one year before being exposed to OA and grazing in a laboratory experiment for two months. Space occupying organisms were identified and pooled into six functional groups: calcified invertebrates, non-calcified invertebrates, calcified algae, fleshy algae, sediment, and bare space for subsequent analyses of community structure. Interestingly, communities that developed on separate tile racks were unique, despite being deployed close in space, and further changes in community structure in response to OA and grazing depended on this initial community state. On Rack 1, we found significant effects of both pCO2 and grazing with elevated pCO2 increasing cover of fleshy algae, but sea urchin grazers decreasing cover of fleshy algae. On Rack 2, we found a ~ 35% higher percent cover of sediment on tiles reared in ambient pCO2 but observed ~27% higher cover of bare space in the high pCO2 conditions. On Rack 3, we found an average of 45% lower percent cover of calcified sessile invertebrates at ambient pCO2 than in high pCO2 treatments on Rack 3. Net community calcification was 137% lower in elevated pCO2 treatments. Kelp sporophyte densities on tiles without urchins were 74% higher than on tiles with urchins and kelp densities were highest in the elevated pCO2 treatment. Urchin growth and grazing rates were 49% and 126% higher under ambient than high pCO2 conditions. This study highlights consistent negative impacts of OA on community processes such as calcification and grazing rates, even though impacts on community structure were highly context-dependent. 

Experimental field cultivation of the agar yielding red alga Gracilaria edulis was carried out at Valinokkam Bay from May 1992 to April 1994 at 1.5 to 3.0 m depths using 2x2 m size coir rope nets fabricated with 1" thick coir ropes and 1" thick long line coir ropes. The seedlings cultured on nets and long line ropes during May to December in 1992 and 1993 degenerated due to sedimentation and low light intensity. The growth of G. edulis seedlings from January to April during 1993 and 1994 was good and reached harvestable size of 14.4 cm and 22.9 cm (mean length) after 45 and 90 days respectively. Harvest could not be made, as many of the grown up plants were grazed by fishes. Data collected on environmental and hydrological parameters from the culture site at fortnightly interval were correlated with the growth of cultured seaweed. The result obtained in this experiment is compared with the results on the experimental field cultivation of G.edulis carried out in the near shore areas of Mandapam and lagoon of Minicoy and Lakshadweep.

Experimental culture of Gracilaria was done in the Kovalam Backwaters at the Mariculture Centre, Muttukadu, Tamil Nadu. The study, conducted over two years, revealed that the period June to March was condusive to growth. The rate of growth was better in the open, unenclosed area than in ponds. Growth was best during the period June to September. The potential yield in the different growing seasons has been estimated for the open area as well as ponds. The relation between the growth of seaweeds and some environmental conditions in the farm is discussed. A strategy is suggested for the continuous culture and domestication of this species in the area.