养殖水体环境参数随潮汐变化特征及相关性分析——以湛江特呈岛东近岸海域为例

利用2018年4-5月在湛江特呈岛东边海域养殖区内测定的数据,以及海事服务网提供的潮汐数据,分析了研究区域潮汐、流速和流向的变化规律,研究了溶解氧(Dissolved Oxygen,DO)、化学需氧量CODMn(Chemical Oxygen Demand)、二氧化碳CO2浓度和pH等海水环境参数随潮汐变化的特征以及相关性,建立了分别利用DO和pH值来估算海水CO2浓度的新算法,平均估算精度分别达到90%和95%。分析结果表明:(1)研究区域呈现不规则半日潮,流速随潮汐变化分为正相关和负相关两种类型;流向随着潮汐变化基本是东南与西北向;(2) CODMn的变化完全取决于涨落潮过程,涨潮时CODMn值逐渐下降,而落潮过程CODMn值逐渐上升;(3) CO2浓度呈现出明显的日变化,在午后数值达到最低值,不完全受制于潮汐过程的控制;(4) DO和pH两者的变化趋势高度一致,其变化过程与CO2浓度变化过程正好相反;(5)同一地点的海洋环境参数随潮汐涨落有很大的变异性,因而在进行空间大面海洋环境参数调查时,用某时刻的值代表该点的全天情况会出现较大的误差。

Analysis on the relationship of aquaculture water environment parameters with tidal characteristics in marine aquaculture areas: A case study at the east sea area of Techeng Island of Zhanjiang

In this study, we used the measured data in the marine aquaculture area at the east of Techeng Island of Zhanjiang in April to May 2018, and the tide data provided by China Shipping Service. We first analyzed the tides, current velocity, and current direction in the studied area. We then analyzed the characteristics of the tide-induced variation of biochemical parameters, including dissolved oxygen (DO), carbon dioxide concentration (CO2), and pH. The relationship between the parameters was also studied. Additionally, we established algorithms to estimate the CO2 concentration by using DO and pH, respectively. This provides a new method to estimate the CO2 concentration. The accuracy of the DO-based and pH-based algorithms is 90% and 95%, respectively. The analyses show the following results: (1) In the studied area, the tides are irregular semidiurnal tides; the current velocity was positively and negatively correlated with the tides; the direction of the current was mainly southeastward and northwestward; (2) the variation of the CODmn is determined by the tides; CODMn decreased during rising tides, while CODMn increased during falling tides; (3) CO2 shows clear diurnal variation; the value of CO2 was at lowest in the afternoon, which was not entirely controlled by the tides; (4) the variation tendencies of DO and pH were highly consistent, which was opposite to the variation tendency of CO2;(5) it is concluded that biochemical parameters at the same location exhibit large variations associated with tides. Therefore, in the surveys of biochemical parameters of large spatial coverage, large errors may occur when a value at a certain time is used to represent the value of the whole day.