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的新兵来源，这个问题涉及到确定幼虫运输过程。该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。它将侧重于内潮涌潮，这种涌潮首先使温跃层露出水面，并使近岸地表水向近海迁移。然后，几个小时后，水流逆转，密集的冷水迁移到离岸，温暖的水返回海岸-由温暖的钻孔前缘引导。为了解决潮汐和累积问题，将采用一种自适应取样方案，即在用遥测系统遥测到内潮涌潮时开始取样。 本文将检验在辐合流锋面上聚集是由于仔鱼逆着下涌流主动游动所致的行为假说。这一假说认为，聚集在汇聚流和下降流输送锋上的颗粒物，其方向应与下降流相反。这将通过用系泊的温度记录仪和多普勒海流计阵列观察锋面的水平会聚和下降流，以及通过观察会聚锋面和锋面外的原位幼虫方向来进行测试。幼虫的方位将用高分辨率的视频浮游生物记录仪（VPR）观察。对于锋面积累过程，将检验锋面幼虫的起源是在传播的内孔暖锋的近海（例如，与陆上起源相反）的想法。这一假说预测，锋面离岸的幼虫浓度远大于锋面岸上的幼虫浓度，锋面u后的流速大于锋面c的前进速度（传播速度）。这将通过在锋面上取样幼虫浓度，观察锋面的相速度和环流，以及通过在锋面周围重新租赁漂流者进行实验来进行测试。对于低频强迫，将研究两个相关的观点.首先，内潮涌潮对幼虫的输送强度取决于由远距离或局部风驱动的上升流引起的温跃层的上升和露出，将通过每日藤壶沉降测量、三个深度温度的时间序列、多普勒流速计观测的流速以及上升流事件期间的密集幼虫取样来检验。第二个假设，即加州州拉霍亚的幼虫运输和温度场的低频变率与下加利福尼亚海岸向北的传播事件有关，将用拉霍亚的每日藤壶沉降监测、AVHRR海表温度卫星资料以及拉霍亚和拉霍亚以南三个地点的风、温度和压力的时间序列进行检验。

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.