Reproductive patterns and secondary production of Gammaropsis japonicus (Crustacea, Amphipoda) on the seagrass Zostera marina of Korea

Abstract

Seagrass beds are diverse and productive components of coastal ecosystems. Amphipods often comprise a major component of their invertebrate fauna and may be among the most important secondary producers. The life history and production of the amphipod Gammaropsis japonicus were investigated monthly for 1 year on a seagrass bed (Zostera marina L.) in Gwangyang Bay, southern Korea. Population density of G. japonicus was closely correlated with seagrass standing crop (P \ 0.05), suggesting that there is a biological interaction between these two groups. The life-history pattern was annual and iteroparous with two principal periods of juvenile recruitment during the year; in spring (May to July) and fall (November to December). The mean body length of adults including ovigerous females was larger in the spring breeding period than in the fall and overall sex ratio was female-biased. The brood size and egg volume were positively related to body length of ovigerous females. At any given female size, egg volume was significantly larger in the fall breeding than in the spring, whereas brood size in the spring breeding was significantly larger than that in the fall. The brood volume of females between the two breeding periods was much greater in the fall than in the spring, suggesting higher reproductive effort during the fall breeding period. Annual biomass of G. japonicus was 2.16 g DW m -2 yr -1 and was higher in the spring than in the fall breeding periods. The annual secondary production (14.59 g DW m -2 yr -1 ) was higher than those observed for other amphipods inhabiting seagrass beds. However, annual productivity to biomass (P/B) ratio, at 6.74, was lower than those recorded previously in both temperate and tropical seagrass beds because the number of generations decreases the P/B ratio. The combination of high abundance and production suggests an important role for G. japonicus in the seagrass beds ecosystem as a trophic link from primary producers to higher consumers.

Seasonal dynamics of prey size mediate complementary functions of mussel beds and seagrass habitats for an avian predator

“…Crab taxa in addition to M. magister likely display similar seasonal patterns in size structure, because water temperature limits the main period of growth to about March through September (McMillan et al 1995). Further, most crustacean taxa may similarly attain greatest body sizes during spring and summer (Sparrevik & Leonardsson 1999, Jeong et al 2009). As was likely the case for the surf scoters in our study, increased mobility of their crustacean prey meant reduced capture success.…”

Factoring scales of spatial and temporal variation in fish abundance in a subtropical estuary

“…Seasonality in solar irradiance and temperature in these mid-latitudes drive peaks of productivity during spring and summer and lower production during late fall and winter (Day et al 1989, Murrell & Lores 2004, Strydom & d'Hotman 2005, Jeong et al 2009). Long-term ecological studies carried out in Patos Lagoon Estuary clearly show such seasonal pulses in both primary and secondary production .…”

Abundance and Distributional Patterns of Benthic Peracarid Crustaceans From the Atlantic Sector of the Southern Ocean and Weddell Sea

“…Burrows built by sediment-living peracarids allow oxygenated water to pass through the sediment layer, consequently promoting the mineralization of organic matter by other organisms (Pelegrí and Blackburn, 1994;Lehtonen and Andersin, 1998). Furthermore, peracarid crustaceans can also directly consume organic matter as deposit-feeders and also feed on dead organisms from the sea bottom as scavengers; the assimilated biomass can be then transferred to the higher trophic levels via direct consumption (Jeong et al, 2009;Thiel and Hinojosa, 2009;Duffy et al, 2012). Peracarids are also an important source of food for benthic organisms as well as pelagic fauna such as fish and squid (Mouat et al, 2001;Padovani et al, 2012;Xavier et al, 2020).…”