Components of Larval Transport: Larval Behavior and Variability in Physical Transport

海洋生态学的一个主要问题是浅水开放种群的新成员来源，这个问题涉及到幼虫运输过程的确定。本项目将研究幼虫运输的三个组成部分：幼虫行为、幼虫在运输前沿的积累以及低频调制对幼虫运输的影响。它将侧重于内部潮汐孔，它首先产生温跃层的露头和近岸地表水的离岸迁移。然后，几个小时后，水流逆转，密集的冷水向海岸移动，而温暖的水在温暖的钻孔锋的引导下返回海岸。为了解决行为和积累问题，将采用自适应采样方案，即在用遥测系统远程探测到内部潮孔时开始采样。将对具有汇聚流的锋面聚集的行为假设进行验证，该假设是由于幼虫主动游向下行流而导致的。该假说预测，在辐合流和下行流输送锋中聚集的幼虫应朝向下行流方向。这将通过使用温度记录仪和多普勒电流计的固定射线观测锋面的水平辐合流和下行流，以及通过观察辐合锋和锋面外的原位幼虫取向来验证。将用高分辨率视频浮游生物记录仪（VPR）观察幼虫的方向。对于锋面积累过程，锋面幼虫的起源是在传播的内部孔暖锋的近海（例如，相对于陆上起源）的想法将得到检验。这一假设预测锋面近海的幼虫浓度远远大于锋面陆上的幼虫浓度，锋面u后面的当前速度比锋面c的前进速度（传播速度）快。这将通过采样锋面上的幼虫浓度，通过观察锋面的相位速度和循环，以及通过在锋面周围进行实验来验证。对于低频强迫，我们将研究两个相关的观点。首先，内部潮汐孔的幼虫运输强度取决于由远程或本地风驱动的上升流引起的温跃层的隆起和突出，将通过每日藤壶沉降测量、三个深度的温度时间序列、用多普勒电流计观察的洋流和上升流事件期间的大量幼虫取样来进行测试。第二个假设是，加州拉霍亚幼虫运输和温度场的低频变化与来自下加利福尼亚州海岸的北繁殖事件有关，该假设将通过拉霍亚的每日barnacle沉降监测、AVHRR海面温度卫星数据以及拉霍亚和拉霍亚南部三个地点的风、温度和压力时间序列进行验证。

A major question in marine ecology is the source of recruits in shallow-water open populations, a question that involves identification of the larval transport process. This project will work on three components of larval transport: larval behavior, larval accumulation in transporting fronts, and the effects of low-frequency modulation on larval transport. It will focus on internal tidal bores, which first produce outcropping of the thermocline and the offshore migration of near-shore surface water. Then, a few hours later, the flow reverses, the dense cold water migrates off-shore, and warm water returns to the shore-lead by a warm bore front. For resolving the be-havioral and accumulation questions, an adaptive sampling scheme will be used, where sampling is initiated when internal tidal bores are remotely detected with a telemetry system. The behavioral hypothesis that accu-mulation in fronts with convergent currents result from larvae swimming actively against the down-welling currents will be tested. The hypothesis predicts that lar-vae that accumulate in transporting fronts with convergent and downwelling currents should ori-ent against the downwelling flow. This will be tested by observing horizontal convergent and downwelling currents in fronts with moored ar-rays of temperature loggers and Doppler current meters, and by observing in situ larval orientation in convergent fronts and outside the fronts. Larval orientation will be observed with a high-resolution Video Plankton Recorder, the VPR. For the frontal accumulation process, the idea that the origin of frontal larvae is offshore of the propagating internal bore warm fronts (e.g. as op-posed to onshore origin) will be tested. This hypothesis predicts that larval concentration offshore of the fronts is much larger than the larval concentration onshore of the fronts, and that the current speed behind the front u is faster than the rate of advance (propaga-tion speed) of the front c. This will be tested by sampling larval concentration across the fronts, by observing the front's phase speed and circulation, and by conducting experiments re-leasing drifters around the fronts. For the low- frequency forcing, two related ideas will be investigated. First, the intensity of larval transport by inter-nal tidal bores depends on the raising and out-cropping of the thermocline by remote or local wind driven upwelling, will be tested with daily barnacle settlement measurements, time se-ries of temperature at three depths, currents ob-served with a Doppler current meter, and intense larval sampling during upwelling events. The sec-ond hypothesis, low-frequency variabil-ity in larval transport and temperature field at La Jolla, California is related to northward propa-gating events from the Baja California coast, will be tested with daily barnacle settlement moni-toring in La Jolla, AVHRR sea-surface temperature satellite data, and time series of wind, tempera-ture, and pressure in La Jolla and three locations South of La Jolla.