First Leg. Cruise LARBAJA I. (Larvae in Alta and Baja California) August 1997. Participants: David Field, Bertha Lavaniegos, Jesœs Pineda, HŽctor Lozano, Patricia Rojo, Erika Lawson, Sam, Jim, TBA undergraduate student and Res. Tech. Narrative This leg will consist of a) Two 24 hour plankton/CTD yo-yoing stations. b) One CTD cross-shore transect at stations every ca. 2.5 km c) Six stations of larval sampling. d) One yo-yoing station at 350 m. e) Mooring recovery work.Day Activity 14 8 AM Depart towards 30 m station position 32¡ 46Õ 31Ó- 117¡ 16Õ 55Ó 10 AM Start 24 h vertical migration / CTD yo-yoing work. 15 10 AM Finish works at 30 m station. Steam towards CTD transect station No. 1 position 32¡ 46Õ 31Ó-117¡16Õ 17Ó(or longitude as shallow as possible). 11 AM Start CTD transect. Occupy stations: 1. 32¡46Õ30Ó - 117¡ 16Õ17Ó 2. 32¡46Õ30Ó - 117¡ 17Õ53Ó 3. 32¡46Õ30Ó - 117¡ 19Õ29Ó 4. 32¡46Õ30Ó - 117¡ 21Õ5Ó 5. 32¡46Õ30Ó - 117¡ 22Õ41Ó 6. 32¡46Õ30Ó - 117¡ 25Õ54Ó 7. 32¡46Õ30Ó - 117¡ 27Õ30Ó 8. 32¡46Õ30Ó - 117¡ 29Õ6Ó 9. 32¡46Õ30Ó - 117¡ 30Õ43Ó 10. 32¡46Õ30Ó - 117¡ 32Õ19Ó 11. 32¡46Õ30Ó - 117¡ 33Õ55Ó 12. 32¡46Õ30Ó Ð 117¡ 35Õ51Ó 8 PM Arrive SD Trough, Station position 32¡46Õ30Ó - 117¡ 35Õ51Ó. Start 24 h CTD plankton sampling and CTD yo yoing. 16 8 PM Finish CTD yo-yoing work and vertical migration work. Steam to 350 m station Position 32¡44Õ45Ó-117¡ 23Õ 1Ó 10 PM Start CTD yo-yoing work at 350 m station. 17 6 AM Head onshore, position 32¡ 42Õ 31Ó- 117¡ 17Õ 12Ó. Start performing 6 daylight larval samples. Station positions are: 1. 32¡ 42Õ 31Ó-117¡ 17Õ 12Ó 2. 32¡ 46Õ 12Ó-117¡ 17Õ 43Ó 3. 32¡ 47Õ 25Ó-117¡ 18Õ 14Ó 4. 32¡ 48Õ 36Ó-117¡ 18Õ 50Ó 5. 32¡ 51Õ 16Ó-117¡ 18Õ 17Ó 6. 32¡ 53Õ 24Ó-117¡ 16Õ 25Ó 6 PM Finish daylight larval sampling work. Steam back to 350 m station, position 32¡44Õ45Ó - 117¡ 23Õ 1Ó 8 PM Begin CTD yo-yoing at 350 m. 18 6 AM Finish CTD yo-yoing work. 6 AM Rendezvous with small boat from SIO to pick up mooring crew. 7 AM Start mooring recovery at 350 m station position 32¡44Õ45Ó - 117¡ 23Õ 1Ó (?) 9 AM Proceed to 500 m station position __________________ for mooring recovery. 8 PM Finish Mooring work. Open for local activities. Arrive San Diego before 8 AM the 19th. Second Leg. Cruise Larbaja I. Participants: David Field, Bertha Lavaniegos, Jesœs Pineda, Paty Rojo, Myrl Hendershott, Jason Foat, TBA undergraduate student, Guillermo GutiŽrrez Velasco, Julio Candela, Alejandro ParŽs. NARRATIVE There will be 3 types of works: 1. 10 CTD transects from Point Loma, USA to San Miguel, Mexico. Latitudes are 32¡ 40.00 ' 32¡ 35.00 ' 32¡ 30.00 ' 32¡ 25.00 ' 32¡ 20.00 ' 32¡ 15.00 ' 32¡ 10.00 ' 32¡ 05.00 ' 32¡ 00.00 ' 31¡ 55.00 ' 2. Two 24 h vertical migration studies, in shallow (30 m) and deep (>800 m) stations. 3. 6 samples of vertical distribution in ~50-60 m water depth. CTD transects. There will be short (30 km) and long (35 km) transects. Short transects will include stations at 1.5, 5, 10, 15, 20, 25 and 30 km offshore. Long transects will include the same plus a station at 35 km. Transects will be separated by 5 min.. 24 h Stations. Larvae will be sampled every 4 hours. 0, 4, 8, 12, 16, 20, 0. Shallow station. 4 depths per sample. Deep-station. 5 depths per sample. Larval vertical distribution: 6 daylight samples of larvae will be obtained up to at 40m water depths (6 depths.). Schedule. August 1997. Day Activity 20 8 AM Steam towards Point Loma, position 32¡40Õ00Ó- 117¼ 14' 51Ó 9 AM Start CTD transects. See below for positions. 21 9 AM (elapsed 24 h). Continue CTD transects. 22 9 AM (elapsed 48 h). Continue CTD transects. 23 4 AM (elapsed 2 days 16 h). Finish CTD transects in San Miguel East. 4 AM Steam North, position 32¡00Õ30Ó-116¡53Õ30Ó(La Salina/Medio Camino). 6 AM Perform larval samples at: 1. 32¡00Õ30Ó-116¡53Õ30Ó 2. 32¡02Õ00Ó-116¡54Õ20Ó 3. 32¡08Õ40Ó- 116¡56Õ10Ó 4. 32¡09Õ50Ó- 116¡56Õ20Ó 5. 32¡11Õ00Ó- 116¡56Õ20Ó 6. 32¡12Õ00Ó-116¡56Õ20Ó 6 PM Finish larval samples. Steam towards 30 m / 24 h Station, position 32¡10Õ00-116¡55Õ00Ó 7 PM Occupy and start 24 h plankton Ð migration / CTD yo-yoing station. 24 7 PM Finish 24 h station. 7 PM Steam towards offshore 24 h station, position 32¡10Õ00Ó-117¡17Õ00Ó 10 PM Start 24 h Plankton Ð migration / CTD yo-yoing station. 25 10 PM Finish 24 h station. 10 PM Navigate towards San Diego. Arrive San Diego before 8 AM the 26th 26 Day open for WinantÕs search-of-mooring activities. 27 Day open for WinantÕs search-of-mooring activities. CTD transect stations:
Introduction
The research that would be performed in the proposed cruise is part of the project "Onshore transport of planktonic larvae by internal tidal bores". This project is funded by the National Science Foundation and it has a single Principal Investigator, Jesús Pineda.
Our research focuses on a physical-transport mechanism that may have important consequences for coastal natural resources. The young (larvae) of many marine organisms that live associated to the seafloor, such as clams, mussels, shrimps, oysters, etc. are minuscule and drift free at the mercy of currents. The juvenile larval phase lasts from a few hours to several months, depending on the species. At the end of this period, the juveniles must find a suitable site or habitat to settle and grow into adults, but they are often found very far from these suitable habitats. These juveniles depend on the "right" currents to return to the sites where they can complete their life cycle. Currents are very important for these species because, for example, without appropriate currents, sites which are otherwise suitable for adult growth would not sustain adult populations. A critical question in shallow water ecology, then, is to identify the mechanisms that dominate the transport of larvae to adult habitats.
Hypothesis
Our study is investigating a hypothesis that would explain different rates of transport of young organisms to different coastal areas. The hypothesis invokes internal waves, which are waves that travel inside the ocean at the interface between deeper, colder water, and surface, warmer water. It explains that water (and larvae) can be moved towards the shore by the breaking of internal waves (Pineda, 1991; 1994). The hypothesis explains that when there is no warm/cold interface --less "stratification"-- there would be less transport of larvae. Sites that for some reason do not develop a warm/cold interface --strong stratification- would receive less larvae than sites where there is a strong warm/cold interface, strong stratification (Pineda, 1996). We have located 2 sites that fit our description, and preliminary results show low number of larvae arriving at the site with a weak warm/cold interface, but very high numbers arriving at the one with a strong warm/cold interface. One site is located in La Jolla, California, USA, while the other, "Las Olas", is just North of Ensenada, Baja California, Mexico.
Objectives
The existence of zones that differ in stratification along the northern Baja-California/southern Alta-California coast implies that there must be sites that differ consistently in hydrography.
The objectives for this cruise are
(1) To identify and map the different "hydrographic" areas along the northern Baja California coast -the identification and mapping based on the hydrographic characteristics of the zones (e.g. temperature and salinity).
(2) To find whether different zooplankton (drifting small organisms) and larval assemblages occur in different regions along the coast corresponding to zones with different hydrography.
(3) To find whether vertical distribution of abundant micro-zooplankton as well as selected invertebrate species (barnacles Chthamalus spp. and Pollicipes polymerus, bryozoans Membranipora membranacea and sea anemones Anthopleura spp.) differs in the hypothetically different hydrographic zones. Vertical distribution is important because different transport mechanisms operate at different depths of the water column.
Methods
In order to address these questions, we propose sampling several transects perpendicular to the shoreline. The instruments and devices that would be used are all standard in Oceanographic Research.
(1) Hydrography.- To address objective No. 1 we would sample the hydrography -temperature and salinity- and currents. The hydrography would be obtained with a Conductivity-Temperature-Depth ("CTD") profiler, an electronic instrument that measures temperature and conductivity (a proxy for salinity). Acoustic-Doppler-Current-Profiler (ADCP) current measurements would be led by our Mexican colleague Dr. Julio Candela (see below), and they would be obtained with the ship-onboard ADCP. We would cover stations in the coastal Pacific Ocean from North of Ensenada, Baja California, Mexico, to close of the US-MEXICO international border, in Mexico. The stations would be taken along 12 transects perpendicular to the coastline (Figure 1). We plan about 120 stations (10 stations per transect) where we would lower the CTD and sample depth profiles of temperature and conductivity in transects perpendicular to the coastline.
(2) Zooplankton and larval composition. We would sample zooplankton, including larvae, in several stations. The number of stations would be determined by the number of distinct hydrographic zones. We would obtain 5 samples in each zone, and we expect to find at least 3 different zones. This effort would be led by Dr. Bertha Lavaniegos, a Mexican colleague. Zooplankton and larvae would be sampled with a small mesh-net in integrated tows (surface to 15 meters water depth ). We tentatively plan to sample ca. 15 m3 water per each tow.
(2) Zooplankton and larval vertical distribution. We would sample zooplankton with a water-pump to assess vertical distribution. We would sample ca. 3m3 of water at surface, 2, 6, 12, and 18 meters depths. As with the zooplankton and larval composition section, we would sample in the different hydrographic zones, with 3 samples at all depths per each zone. This effort would be led by Bertha Lavaniegos and J. Pineda.
Timetable
The ship would leave from the port of San Diego on 26 August 1997, enter Mexican waters on the same day, 26 August 1997, workout the transects from North to South, and then return North, and leave Mexican waters on 8 September 1997.
Justification
Importance of this study.- Understanding larval transport and larval transport variability is a critical issue in fisheries management of exploited marine invertebrates -such as abalone Haliotis spp, seaurchins Strongylocentrotus spp, Pacific lobster Panulirus interruptus- and in the design of coastal marine reserves. As pointed above, the reason why larval transport is so important is because in 2-phase life-cycle species local abundance is often dependent on larval transport processes rather than on local-population reproductive-parameters. Sites that are otherwise suitable for the growth and reproduction of adults may not have high adult densities because currents do not transport larvae there. Understanding of larval transport is also critical in designing marine reserves designed to preserve nearshore natural resources. Larval transport varies alongshore, and some populations are "sink" populations maintained only by larvae produced by adults occurring elsewhere, and whose larval production is wasted. Other populations are "source" populations whose larvae have high probability of landing on suitable habitats. Knowledge of physical transport processes is then obviously important for designing reserve systems. But currents returning juveniles to the shore are not only of societal interest because of management of exploited populations. In a similar manner that currents can transport young marine animals from offshore to coastal sites, currents can also transport human sewage, which is usually disposed offshore at a certain depth off many coastal cities. Transport processes are then critical criteria to select discharge locations.
Why we propose to study Mexican waters- Several factors account for the selection of the study area.
We believe that the benefits of this cruise and collaboration include not only the collaboration itself, which enriches intellectually our scientific work, but also improved understanding of larval transport and possibly improved understanding the management of the coastal zone, all in Mexican coastal waters
Mexican participation
I am currently an Adjunct Professor at CICESE, and a Mexican citizen. Other Mexican collaborators closely involved in this project include:
(1) Dr. Bertha Lavaniegos, Professor, Departamento de Ecología, CICESE. Dr. Lavaniegos will lead the effort in the sampling of the plankton with both the nets and pumps. We are also collaborating with Dr. Lavaniegos in other closely-related coastal research, and this cruise would complement this research.
(2) Dr. Alejandro Parés-Sierra, Professor, Departamento de Oceanografía Física, CICESE.
Dr. Parés-Sierra would assist with the CTD observations. He would also participate in helping understanding the potential physical factors producing the different hydrographic zones. His involvement in this project is also related to our long-term collaborative goal, which is understanding and modelling how global change will impact the population dynamics of marine invertebrates.
(3) Dr. Julio Candela, Professor, Departamento de Oceanografía Física, CICESE.
Dr. Candela was not listed in our previous proposal to the SRE. Dr. Candela has recently expressed interest in joining this cruise, and he was listed a collaborator in the original NSF proposal. Dr. Candela is very experienced in the use of shipboard ADCP, and he will be in charge of this instrument. In addition, he is very interested in the problem of the physical basis of variability in stratification along the Northern Baja California Coast.
All the Mexican participants listed above have compromised in joining the cruise.
Literature cited
Pineda J. (1991) Predictable upwelling and the shoreward transport of planktonic larvae by internal tidal bores. Science (Washington D.C.), 253, 548-551.
Pineda J. (1994a) Internal tidal bores in the nearshore: warm-water fronts, seaward gravity currents and the onshore transport of neustonic larvae. Journal of Marine Research, 52, 427-458.
Pineda J. (1996) Extreme alongshore variability in barnacle settlement. EOS, Transactions, American Geophysical Union, 76, OS94.