江苏海门蛎岈山牡蛎礁恢复工程的生态评估

Ecological assessment of the oyster Crassostrea sikamea population and associated benthic communities on restored oyster reefs along Jiangsu Province coast,China

江苏海门蛎岈山牡蛎礁是我国目前现存的面积最大的潮间带活体牡蛎礁,但由于人类活动干扰及泥沙淤积等原因,该自然牡蛎礁面积不断缩小,影响着该牡蛎礁的生态功能与保护管理。于2013—2014年开展了首期江苏海门蛎岈山牡蛎礁恢复工程,基于生态监测结果评估该牡蛎礁恢复工程的生态效果。多层礁体上活体牡蛎丰度显著高于单层礁体(P<0.05);随着礁体的发育,恢复礁体上牡蛎丰度显著下降(P<0.05)。非参数Kruskal-Wallis检验结果显示,在两个生活周期内(2013-09—2013-11,2014-03—2014-05)牡蛎均呈现快递的生长(Q=10.519,Q=6.527,P<0.05),而在越冬期内(2013-11—2014-03)牡蛎几乎停止了生长(Q=0.35,P>0.05)。随着礁体的发育,恢复牡蛎礁上大型底栖动物群落的物种丰度并没有增加,但其平均总密度和总生物量均呈现显著性的增长(P<0.05);礁体构建后1a时恢复牡蛎礁中大型底栖动物的平均总密度和生物量均接近于自然牡蛎礁(P>0.05),但显著高于未恢复区(P<0.05);恢复牡蛎礁与自然牡蛎礁具有显著不同的大型底栖动物群落(ANOSIM,P=0.001)。研究结果表明该牡蛎礁恢复工程取得初步成功。

Oyster reefs are an important coastal habitat providing essential ecosystem services, including water filtration, habitat provisioning, shoreline stabilization, and nutrient retention. The Liyashan oyster reef is located inshore of Dongzhao Port, Haimen County, Jiangsu Province, China. However, the natural intertidal oyster reef is rapidly degrading due to high sedimentation, habitat loss, and overfishing, with its area reduced by 30% during 2003-2013. To protect the important biogenic reef, a restoration project was initiated in 2013-2014. We recycled 100 tons of oyster shells （≥ 6 months） from the oyster aquaculture zone in Xiangshan Bay as substrate （cultch） for oyster larval setting, where 16000 nylon bags （diameter：20 cm, height：50 cm, mesh：2 cm） were filled with old oyster shells. In early July 2013, the oyster shells were placed in the Liyashan waters, creating a habitat for young oysters to attach and grow to ensure their abundance. We constructed 53 small reefs （24 single-layer reefs[SLR] and 29 multi-layer reefs[MLR]） at five restoration sites within the Liyashan area. Oyster abundance was significantly higher in MLR than in SLR at each of the four sampling periods, but showed a significant decline with reef development. The mean shell height of oysters in the restored reef significantly increased during two periods （from September to November 2013, and March to May 2014） （Kruskal-Wallis test, Q=10.519,Q=6.527,P〈0.05）, but oysters stopped growing in the overwintering period （Nov 2013 to March 2014） （Q=0.35,P〉0.05）. Forty-one species of resident benthic macrofauna were recorded at the restored reefs. Although there were few changes in species richness, the mean density and biomass showed significant increases with reef development that were similar to the adjacent natural oyster reef, but significantly higher than at the non-restored zone. The mean total density and biomass of benthic communities were 5.1 and 3.1 times higher, respectively, at restored than at non-restored reefs.MDS plots showed that resident benthic communities differed significantly between the restored and adjacent natural reefs （ANOSIM, P=0.001）, which were mainly attributed to higher densities of sipunculid worms （Phascolosoma esculenta）, rock snails （Thais luteostoma）, polychaete worms （Perinereis nuntia）, and Asian shore crabs （Hemigrapsus sinensis）. Oyster reef restoration in Jiangsu Province was considered to be successful, improving the oyster population, reef area and density, and biomass of resident macrofauna.