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

海洋生态学中的一个主要问题是浅水开放种群中新兵的来源，这一问题涉及幼虫运输过程的识别。这个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。它将把重点放在内部潮汐孔上，这首先会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，稠密的冷水向外迁移，温暖的水回到岸上--在温暖的钻孔锋面的引导下。为了解决行为和蓄积问题，将采用自适应采样方案，当遥测系统远程检测到内部潮汐孔时，开始采样。有收敛流锋面积聚是由于幼虫主动逆流而游的行为假说将得到检验。该假说预测，在汇聚下沉气流的输送锋面上积聚的较大VAE应该与下沉气流相反。这将通过使用温度记录仪和多普勒海流仪的系泊雷达观测锋面上的水平汇聚和下流流，以及在汇聚锋面和锋面外现场观测幼虫的方位来进行测试。幼虫的定位将用高分辨率的浮游生物录像机VPR进行观察。对于锋面积聚过程，将检验锋面幼虫起源于传播的内孔暖锋的近岸(例如，假设为陆上起源)的想法。这一假说预测，锋面近海的幼虫密度远大于锋面岸上的幼虫密度，并且锋面后的水流速度u快于锋面c的推进速度(传播速度)。这将通过对锋面上的幼虫密度进行采样、观察锋面的相速度和环流以及在锋面周围进行再出租漂浮物的实验来检验。对于低频强迫，我们将探讨两个相关的概念。首先，通过内部潮汐孔输送幼虫的强度取决于温跃层的抬高和露出，这取决于远程或本地风驱动的上升流，将通过每日藤壶沉降测量、三个深度的温度时间序列、用多普勒流速仪观测的海流和上升流事件期间密集的幼虫采样来检验。第二个假设，加利福尼亚州拉霍亚幼虫运输和温度场的低频变化与下加利福尼亚州海岸向北推进的事件有关，将用拉霍亚每日藤壶沉降监测、AVHRR海面温度卫星数据以及拉霍亚和拉霍亚以南三个地点的风、温度和气压时间序列进行检验。

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.