Rodusky Andrew J, Sharfstein Bruce, East Therese L, Maki Ryan P
Lake Okeechobee Division, South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, Florida, USA.
Environ Monit Assess. 2005 Nov;110(1-3):87-97. doi: 10.1007/s10661-005-6338-2.
Two boat-based and one in-water sampling method have been used to collect submerged aquatic vegetation (SAV) as part of a long-term monitoring program in Lake Okeechobee, Florida, USA. The boat-based methods consisted of collecting SAV with a ponar dredge, used only to collect Chara, and an oyster tongs-like rake apparatus, used to collect all SAV. The in-water method involved use of a 0.5 m2 PVC quadrat frame deployed by a diver. During summer 2002, SAV biomass samples were collected using all three methods at various sites in the lake to compare between-methods sampling precision. Sites used for these comparisons were selected based on plant type, plant density and sediment type. Statistical comparisons indicated that there were significant (p < or = 0.05) biomass differences in 8 of 15 possible pairwise comparisons between sampling method biomass means. In four of the eight comparisons, significantly higher biomass mean values were obtained using the quadrat frame. In three of the remaining four comparisons, significantly higher biomass mean values were obtained with the rake apparatus. For the fourth comparison, a significantly higher biomass mean value was obtained with the ponar dredge. Three of the four relationships between SAV biomass collected by the rake and the quadrat and the rake and the quadrat/ponar dredge were statistically significant, linear and explained between 67 and 78% of the biomass variability. There were no significant differences between regression coefficients or elevations for these relationships, therefore these regressions estimated the same population regression. The population regression coefficient was 0.95, suggesting that the quadrat and ponar over-sampled relative to the rake, but the amount of this over-sampling was very small. Since there was no consistent pattern in the sampling method which yielded the significantly different biomass values and there were no significant differences in sampling precision across a range of plant species, plant densities and two sediment types, the boat-based rake method appears to be a suitable replacement for the previously used ponar dredge and quadrat methods, when in-lake measurements are not practical.
在美国佛罗里达州奥基乔比湖的一项长期监测项目中，采用了两种基于船的采样方法和一种水下采样方法来采集沉水水生植被（SAV）。基于船的方法包括用一种仅用于采集轮藻的ponar采泥器采集SAV，以及用一种类似牡蛎夹的耙式器具采集所有SAV。水下方法是由潜水员部署一个0.5平方米的PVC样方框。2002年夏季，在该湖的不同地点使用这三种方法采集了SAV生物量样本，以比较不同方法的采样精度。用于这些比较的地点是根据植物类型、植物密度和沉积物类型选择的。统计比较表明，在采样方法生物量均值之间15种可能的成对比较中，有8种存在显著（p≤0.05）的生物量差异。在这8种比较中的4种中，使用样方框获得的生物量均值显著更高。在其余4种比较中的3种中，用耙式器具获得的生物量均值显著更高。对于第4种比较，用ponar采泥器获得的生物量均值显著更高。耙式器具与样方框以及耙式器具与样方框/Ponar采泥器采集的SAV生物量之间的4种关系中有3种具有统计学意义、呈线性且解释了67%至78%的生物量变异性。这些关系的回归系数或截距没有显著差异，因此这些回归估计的是相同的总体回归。总体回归系数为0.95，这表明样方框和ponar相对于耙式器具存在过采样，但这种过采样的量非常小。由于在产生显著不同生物量值的采样方法中没有一致的模式，并且在一系列植物物种、植物密度和两种沉积物类型中采样精度没有显著差异，所以当在湖内测量不实际时，基于船的耙式方法似乎是先前使用的ponar采泥器和样方框方法的合适替代方法。
