Biomass and productivity of seagrass communities in Exmouth Gulf, Western Australia

In August/September 1995, visual surveys of seagrass abundance were undertaken along 47 transects, located along the eastern and western coasts of Exmouth Gulf. Transects extended from the shoreward to the seaward border of the zone vegetated with macrophytes. Spot checks were made at approximately every 10m to 20m along each transect and the percent cover and type of vegetation (identified to genus, where possible) were recorded. When there was taxonomic uncertainty, voucher specimens were taken for later identification.Destructive sampling was carried out along transects at three sites: Tent Island (2 transects), Simpson Island (2 transects) and Exmouth Town (3 transects). Five or ten 0.25m² quadrats were randomly placed along each 50m transect. Quadrats were photographed, the percent cover of macrophytes was estimated and the density of seagrass was measured. From each site, the species composition of 5 Cymodocea samples was quantified.All biomass was removed from each quadrat including seagrass roots and rhizomes to a depth of 20cm. Below ground material from Thalassodendron ciliatum was not collected. After drying samples for 48 hours at 70°C, epiphytes were removed and the remaining sample was ashed for 18 hours at 450°C and the dry weight determined. Subsamples were analysed for total carbon and nitrogen.At the three sites, all distal shoots of Cymodocea serrulata occurring along a 20m transect were tagged and at Exmouth, 25 shoots of Thalassodendron ciliatum were also tagged. After 6, 12 or 16 days (depending on the site), complete shoots were collected, measured and divided into new and old parts of leaves. The material was then dried and analysed for carbon and nitrogen content.
This research was initiated to collect data on biomass and production rates of seagrasses to assess their potential contribution to the food webs of Exmouth Gulf.

1995年8月至9月，研究人员在埃克斯茅斯湾（Exmouth Gulf）东西两岸布设的47条样带（transect）上开展海草丰度目视调查。样带从大型植物（macrophyte）覆盖带的近岸边界延伸至远岸边界。沿每条样带每10米至20米设置定点抽查，记录植被盖度百分比与植被类型（尽可能鉴定至属级分类单元）。若存在分类学不确定性，则采集凭证标本（voucher specimen）用于后续鉴定。
破坏性采样在三个样地的样带上开展：坦特岛（Tent Island，布设2条样带）、辛普森岛（Simpson Island，布设2条样带）与埃克斯茅斯镇（Exmouth Town，布设3条样带）。每条50米长的样带随机布设5个或10个0.25平方米的样方（quadrat）。对样方进行拍照，估算大型植物盖度百分比，并测定海草密度。每个样地均定量分析5份丝粉藻属（Cymodocea）样品的物种组成。
从每个样方中移除全部生物量（biomass），包括海草根与根状茎（rhizome），采样深度达20厘米；但未采集纤毛节鞘藻（Thalassodendron ciliatum）的地下部分。将样品置于70℃下烘干48小时后，去除附生生物（epiphyte），剩余样品在450℃下灰化18小时，测定其干重。随后对分样开展总碳与总氮含量分析。
在三个样地中，对沿20米样带分布的所有锯齿丝粉藻（Cymodocea serrulata）顶枝（distal shoot）进行标记；在埃克斯茅斯样地，同时标记25株纤毛节鞘藻（Thalassodendron ciliatum）。经过6天、12天或16天（依样地差异而定）后，采集完整枝条，测量其形态参数并分为新生叶片与老叶部分。将样品烘干后，分析其碳与氮含量。
本研究旨在收集海草生物量与生产力相关数据，以评估其对埃克斯茅斯湾食物网的潜在贡献。