Eastern Tropical Pacific Ocean Research Articles

Review of potential line-transect methodologies for estimating abundance of dolphin stocks in the eastern tropical Pacific

A twelve-year hiatus in fishery-independent marine mammal surveys in the eastern tropical Pacific Ocean (ETP), combined with a mandate to monitor dolphin stock status under international agreements and the need for reliable stock status information to set dolphin bycatch limits in the tuna purse-seine fishery, has renewed debate about how best to assess and monitor ETP dolphin stock status. The high cost of replicating previous ship-based surveys has intensified this debate. In this review, transect methods for estimating animal abundance from dedicated research surveys are considered, with a focus on both contemporary and potential methods suitable for surveying large areas for dolphin species that can form large, multi-species aggregations. Covered in this review are potential improvements to the previous ship-based survey methodology, other ship-based methods, alternative approaches based on high-resolution imagery and passive acoustics, and combinations of ship-based and alternative approaches. It is concluded that for immediate management needs, ship-based surveys, with some suggested modifications to improve precision, are the only reliable option despite their high cost. However, it is recommended that a top research priority should be development of composite methods. Pilot studies on the use of high-resolution imagery and passive acoustics for development of indices of relative abundance to be used in composite methods should be part of any future ship-based survey efforts.

Explainable deep learning for insights in El Niño and river flows

The El Niño Southern Oscillation (ENSO) is a semi-periodic fluctuation in sea surface temperature (SST) over the tropical central and eastern Pacific Ocean that influences interannual variability in regional hydrology across the world through long-range dependence or teleconnections. Recent research has demonstrated the value of Deep Learning (DL) methods for improving ENSO prediction as well as Complex Networks (CN) for understanding teleconnections. However, gaps in predictive understanding of ENSO-driven river flows include the black box nature of DL, the use of simple ENSO indices to describe a complex phenomenon and translating DL-based ENSO predictions to river flow predictions. Here we show that eXplainable DL (XDL) methods, based on saliency maps, can extract interpretable predictive information contained in global SST and discover SST information regions and dependence structures relevant for river flows which, in tandem with climate network constructions, enable improved predictive understanding. Our results reveal additional information content in global SST beyond ENSO indices, develop understanding of how SSTs influence river flows, and generate improved river flow prediction, including uncertainty estimation. Observations, reanalysis data, and earth system model simulations are used to demonstrate the value of the XDL-CN based methods for future interannual and decadal scale climate projections.

Seasonal net calcification by secondary calcifiers in coral reefs of the Eastern Tropical Pacific Ocean

Seasonal net calcification by secondary calcifiers in coral reefs of the Eastern Tropical Pacific Ocean

Microplastic contamination and risk assessment in blue shark (Prionace glauca) from the eastern tropical Pacific Ocean.

We quantified the abundance and characteristics of microplastics in the blue shark, Prionace glauca, found in the eastern tropical Pacific Ocean and investigated the potential microplastic pollution risks. Microplastics (MPs) were detected in 39.1% of specimens, up to 0.15±0.38 items/g wet weight of the posterior part of the pylorus, and were sized 45.87 to 3220.12μm. The majority were fibrous in shape (83.3%) and blue in color (72.2%). Both sexes of sharks had similar MP abundance and characteristics, except for polymers, with polyethylene terephthalate and polypropylene representing the dominant type in males and females, respectively. Most individuals experienced low pollution, but one male P. glauca exhibited a high ecological risk level owing to the high MP abundance and detection of polyvinyl chloride. This study provides an important baseline for the ingestion of microplastics by pelagic shark species and is a preliminary quantitative measure that could be used in future studies of the risk of MPs.

Comparative Analysis between Sea Surface Salinity Derived from SMOS Satellite Retrievals and in Situ Measurements

Validating Sea Surface Salinity (SSS) data has become a key component of the Soil Moisture Ocean Salinity (SMOS) satellite mission. In this study, the gridded SMOS SSS products are compared with in situ SSS data from analyzed products, a ship-based thermosalinograph and a tropical moored buoy array. The comparison was conducted at different spatial and temporal scales. A regional comparison in the Baltic Sea shows that SMOS slightly underestimates the mean SSS values. The influence of river discharge overrides the temperature in the Baltic Sea, bringing larger biases near river mouths in warm seasons. The global comparison with two Optimal Interpolated (OI) gridded in situ products shows consistent large-scale structures. Excluding regions with large SSS biases, the mean ΔSSS between monthly gridded SMOS data and OI in situ data is −0.01 PSU in most open sea areas between 60°S and 60°N, with a mean Root Mean Square Deviation (RMSD) of 0.2 PSU and a mean correlation coefficient of 0.50. An interannual tendency of mean ΔSSS shifting from negative to positive between satellite SSS and in situ SSS has been identified in tropical to mid-latitude seas, especially across the tropical eastern Pacific Ocean. A comparison with collocated buoy salinity shows that on weekly and interannual scales, the SMOS Level 3 (L3) product well captures the SSS variations at the locations of tropical moored buoy arrays and shows similar performance with in situ gridded products. Excluding suspicious buoys, the synergetic analysis of SMOS, SMAP and gridded in situ products is capable of identifying the erroneous data, implying that satellite SSS has the potential to act as a real-time 27 Quality Control (QC) for buoy data.

Interannual Variability of Autumn Precipitation Over the Greater Mekong Subregion

AbstractThis study investigates the interannual variability in autumn precipitation over the Greater Mekong Subregion (GMS) during the period 1981–2019 and its possible causes. Statistical analysis indicates that GMS autumn precipitation showed a seesaw pattern between the central–southern and northeastern GMS over interannual timescales. The tropical sea surface temperature anomalies (SSTAs), reflected in the tropical northeastern Pacific SST index (TNEPI), significantly modulate anomalous GMS autumn precipitation. When the TNEPI is higher than normal, the SSTAs pattern prevails during autumn, with warmer SSTAs in the tropical eastern Pacific and western Indian Ocean, and colder SSTAs in the tropical western Pacific and southeastern Indian Ocean. This SSTAs pattern excites an anomalous anticyclone in the lower troposphere over the central–southern GMS and an anomalous cyclone over the northeastern GMS by the Gill–Matsuno mechanism. Subsequently, the anomalous anticyclone with anomalous descending motion results in below‐normal autumn precipitation over the central–southern GMS via a weakening of the convergence of water vapor from the tropical western Pacific and the Bay of Bengal. The anomalous cyclone on the northern flank of anomalous anticyclone, benefiting from water vapor supply from the Bay of Bengal, leads to above‐normal autumn precipitation over the northeastern GMS. The TNEPI, incorporating signals from the eastern‐Pacific (EP) type of ENSO, Indian Ocean dipole (IOD), and SSTAs associated with the Trans‐Niño index (TNI‐like), shows a stronger relationship with GMS autumn precipitation than individual indexes that describing the EP‐type ENSO, IOD or TNI‐like pattern. Therefore, the TNEPI can be considered an efficient predictor of GMS autumn precipitation.

Two-Way Teleconnections between the Southern Ocean and the Tropical Pacific via a Dynamic Feedback

Abstract Despite substantial global mean warming, surface cooling has occurred in both the tropical eastern Pacific Ocean and the Southern Ocean over the past 40 years, influencing both regional climates and estimates of Earth’s climate sensitivity to rising greenhouse gases. While a tropical influence on the extratropics has been extensively studied in the literature, here we demonstrate that the teleconnection works in the other direction as well, with the southeast Pacific sector of the Southern Ocean exerting a strong influence on the tropical eastern Pacific. Using a slab ocean model, we find that the tropical Pacific sea surface temperature (SST) response to an imposed Southern Ocean surface heat flux forcing is sensitive to the longitudinal location of that forcing, suggesting an atmospheric pathway associated with regional dynamics rather than reflecting a zonal-mean energetic constraint. The transient response shows that an imposed Southern Ocean cooling in the southeast Pacific sector first propagates into the tropics by mean-wind advection. Once tropical Pacific SSTs are perturbed, they then drive remote changes to atmospheric circulation in the extratropics that further enhance both Southern Ocean and tropical cooling. These results suggest a mutually interactive two-way teleconnection between the Southern Ocean and tropical Pacific through atmospheric circulations, and highlight potential impacts on the tropics from the extratropical climate changes over the instrumental record and in the future.

Probable signature whistle production in Atlantic white‐sided (Lagenorhynchus acutus) and short‐beaked common (Delphinus delphis) dolphins near Cape Cod, Massachusetts

Probable signature whistle production in Atlantic white‐sided (<i>Lagenorhynchus acutus</i>) and short‐beaked common (<i>Delphinus delphis</i>) dolphins near Cape Cod, Massachusetts

Key regions in the modulation of seasonal GMST variability by analyzing the two hottest years: 2016 vs. 2020

Following the end of the decadal-warming-hiatus in 2016, the global mean surface temperature (GMST) abruptly showed a 3 yr warming slowdown and peaked again in 2020, overturning the conventional concept that highest GMST occurs with strong El Niño. The high GMST in 2016 was controlled by secular trend and annual variability (ANV). However, the dominator of the sharp GMST rise in 2020 was SCT alone because the ANVs in different seasons canceled each other out in 2020, contributing little to the annual mean GMST. By analyzing the two hottest years, 2016 and 2020, we identified that seasonally varying ANVs are mainly located in Eurasia, North America, the Arctic Ocean, and the tropical eastern Pacific Ocean. Dominance by surface temperatures over the four crucial regions on the subseasonal-to-seasonal (S2S) GMST variations was also observed in 73% of the years during 1982–2021, indicating a potential opportunity to improve the S2S GMST forecast.

Trophic niche partitioning of five sympatric shark species in the tropical eastern Pacific Ocean revealed by multi-tissue fatty acid analysis

Fatty acid (FA) analysis of consumer tissues has recently shown utility in drawing further inferences about trophic niche dynamics of marine predators such as sharks. In this study, we examined liver, plasma, and muscle FAs in five coexisting pelagic sharks (blue (Prionace glauca), silky (Carcharhinus falciformis), bigeye thresher (Alopias superciliosus), pelagic thresher (Alopias pelagicus), and smooth hammerhead (Sphyrna zygaena)) inhabiting the tropical eastern Pacific Ocean. Results showed complex inter- and intra-individual and tissue variation among the five shark species. Based on multivariate analysis of the muscle FAs, P. glauca and C. falciformis have the largest FA niche widths, indicating diverse feeding habits or habitat isolation, whereas A. pelagicus and S. zygaena occupied a narrower niche width, reflecting increased trophic specialization. High percentages of muscle FA niche overlap indicated strong resource competition between S.zygaena and C. falciformis and a degree of dietary isolation by P. glauca. Interpretations of feeding ecology differed based on the analysis of plasma FAs, which could be attributed to higher dietary FA turnover rates. The liver was deemed unsuitable to examine FA niche metrics based on high and unexplained intra-specific variance in liver FAs as well as the unique lipid metabolism in chondrichthyans. Overall, our multi-tissue approach revealed the magnitude of potential competitive interactions among coexisting tropical shark species. It also expanded our understanding of inter-tissue variability and best practices when using FA analysis to estimate trophic niche metrics of sharks.

Movement, Behavior, and Habitat Use of Whale Sharks (Rhincodon typus) in the Tropical Eastern Pacific Ocean

Whale sharks (Rhincodon typus) are found circumglobally in tropical, subtropical, and warm temperate waters, and their known seasonal aggregations and migratory movements are influenced by factors such as ocean currents, thermobiological systems, and patterns of productivity. Several locations in the eastern tropical Pacific Ocean are known habitats for R. typus; Although it has long been known that whale sharks aggregate along the Panama coast, little is known in relation to their movement patterns, behavior, and habitat use. In this study, we investigated the movements and behaviors of R. typus tagged in Panama in relation to oceanographic variables and examined the overlap of foraging habitat and migratory routes with marine protected areas (MPAs), industrial fishing areas, and marine traffic. Satellite tracks from 30 R. typus tagged in the coastal waters of Panama were examined, including nine tags suspicious of earlier detachment. A hidden Markov model was then used to identify different behavioral states (foraging and migrating) and their relationships with environmental variables (sea surface temperature, primary productivity, chlorophyll-a concentrations, and eddy location/speed) Tracks were also superimposed on maps of MPAs, industrial fishing areas, and regional marine vessel traffic to identify the degree of overlap. Rhincodon typus foraged mainly within the Panamanian exclusive economic zone but also moved north and south along the coast and out to the open ocean. Significant differences in environmental conditions were found between sites in which foraging and migrating behaviors were recorded. Higher productivity and chlorophyl concentration were associated with foraging behavior, while higher eddy speeds were observed when sharks migrated. Rhincodon typus used MPAs; however, there was a high degree of overlap between their habitat and areas of industrial fishing and marine vessel traffic. Our results highlight the use of the coastal waters of Panama, oceanic seamounts, and ridges, MPAs and industrial fishing areas by R. typus for foraging and migration. Additionally, our findings highlight the importance of satellite tracking studies for understanding the behavior and habitat use of highly mobile migratory species, such as R. typus.

The Impact of Indonesian Throughflow Constrictions on Eastern Pacific Upwelling and Water‐Mass Transformation

The Indonesian Throughflow (ITF) is a key link in the global ocean overturning circulation. Heat gained from upwelling and watermass transformation in the eastern equatorial Pacific Ocean (PO) is transported through the ITF into the Indian Ocean, ultimately connecting to high-latitude regions of heat loss such as the North Atlantic. However, state-of-the-art General Circulation Models (GCMs) often poorly simulate upwelling, particularly in the eastern Pacific boundary regions. Recent studies have hypothesized that these difficulties may be related to biases in downstream ITF volume and heat transport, whereby insufficient warm surface water from the western PO passes through the ITF, a complex region that is hard to accurately represent in models. Here, we test this hypothesis using a coarse-resolution ocean model by artificially widening the ITF and allowing greater quantities of warm water to exit the western PO. This reduces the Indo-Pacific sea-surface height and pressure gradient biases. Using diagnostics in temperature coordinates, we trace the source of increased ITF warm-water transport to enhanced watermass transformation of cold-to-warm waters in the eastern tropical PO. Additional cool water is brought to the surface in the Cold Tongue region, resulting in an enhancement of surface flux-driven warming. However, we find only limited evidence for changes in upwelling at lower temperatures along the eastern PO margins, considerably less than hypothesized in a previous study. Our experiment provides useful insights to help understand simulated ITF mass and heat transport biases and their links with the tropical PO in GCMs.

Rainfall Variability during El Nino, La Nina and Neutral Years Over Karnataka

The El Niño-Southern Oscillation (ENSO) is a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean. The three phases of the El Niño–Southern Oscillation (ENSO) namely the neutral phase, El Niño and La Niña oscillations. El Niño refers to the above-average sea-surface temperatures that periodically develop across the east-central equatorial Pacific. It represents the warm phase of the ENSO cycle. La Niña refers to the periodic cooling of sea-surface temperatures across the east-central equatorial Pacific. The state of Karnataka is located on a table land in the angle where the Western and Eastern Ghat ranges converge into the Nilgiri hill complex. 41 year (1980-2020) average annual rainfall of Karnataka collected from the rain gauge station located under the farm universities of Karnataka and, SST and SOI data collected from NOAA were used to study the rainfall variability while ENSO events. The El Niño events will deviate the rainy winds towards eastern pacific region causing lesser rainfall on Indian sub-continent or draughts in some years, but when it comes to Karnataka El Niño events have given above average rainfall. There were 8 episodes of excess rainfall and 6 episodes of deficient rainfall during the 14 El Niño episodes, and 3 episodes of excess rainfall and 8 episodes of deficient rainfall during the 11 La Niña episodes. The remaining 16 episodes were neutral years, with 10 episodes having excessive rainfall and the remaining 6 having deficient rainfall. Hence the El Niño episodes is good when compared to La Niña episodes over Karnataka.

The functional ecology of mangrove fishes across the Isthmus of Panama

AbstractAimBiogeographic history and variation in modern environmental conditions can greatly influence local and regional community structure and, more generally, ecosystem functioning. This is clearly exemplified at the Isthmus of Panama where marine communities and environments from the Caribbean Sea and the Tropical Eastern Pacific Ocean differ despite ancient connections during the Miocene and Pleistocene. Here, we compare the functional (implied from traits) and isotopic structure of mangrove fish communities from those two biogeographic regions, which have been separated by the Isthmus of Panama for ~3 my.LocationCaribbean and Pacific coasts of Panama (Eastern Pacific and Caribbean Sea).MethodsWe gathered data on five functional traits (salinity preference, body mass, diet, position in the water column and lifespan) of mangrove fishes from the sampled regions. We also analysed δ13C and δ15C isotopic values and calculated functional isotopic metrics of the most abundant fish species inhabiting mangroves of these two regions.ResultsThe taxonomic composition and functional and trophic diversity differed between the mangrove fish communities of the Caribbean and the Eastern Pacific. Although the species richness of both assemblages was similar, there was very little taxonomic overlap between them: Snooks (Centropomidae) numerically dominated in the Eastern Pacific, whereas grunts (Haemulidae) and snappers (Lutjanidae) dominated in the Caribbean Sea. Functional divergence (FDiv) and isotopic richness (IRic) were higher in the Caribbean than in the Eastern Pacific, indicating differences in the way fishes use mangroves in these areas.Main conclusionsTaxonomic and functional characteristics of mangrove fish assemblages across biogeographic realms can be strongly influenced by local environmental factors (e.g. tidal regimes, the presence of adjacent coastal ecosystems and productivity), and these can override similarities that recent historical connections of faunas might be expected to produce. All such aspects need to be considered when seeking generalizations about ecosystem functioning.

Temporal changes in the epipelagic copepod assemblage at Gorgona Island, Colombian Eastern Tropical Pacific ocean

Temporal variations in the hydrographic conditions of the Eastern Tropical Pacific (ETP) can modulate the assemblage structure of marine organisms, including copepods. While this taxonomic group has been widely recognized as important in the energy flow of the pelagic environment, fundamental ecological aspects are still unknown particularly possible relationships with oceanographic variations that have been described for ETP. In this paper, we evaluated the intra-annual and interannual variation of structure, richness, diversity, and similarity of the epipelagic copepod assemblage of Gorgona Island (Colombian ETP) based on samples collected during six oceanographic campaigns carried out between 2010 and 2016. We found significant changes in the oceanographic conditions and abundance of copepods between periods and years. Seven significant clusters were identified: five for each sampled period and two for the period of October 2010. Ditrichocorycaeus andrewsi, Oncaea clevei, Paracalanus parvus, and Subeucalanus pileatus were the species with the greatest contribution to group formation. Our results suggest that the intra-annual changes in the assemblage of epipelagic copepods recorded in Gorgona Island are a consequence of the displacement of the Intertropical Convergence Zone throughout the ETP during the year. This is due to the fact that during the periods of March they respond to the entry of subsurface waters from the Ensenada de Panama, and during the periods of October respond to the increase of the continental runoff on the pelagic environment of Colombian ETP.

Test-size evolution of the planktonic foraminifer &amp;lt;i&amp;gt;Globorotalia menardii&amp;lt;/i&amp;gt; in the eastern tropical Atlantic since the Late Miocene

Abstract. The mean test size of planktonic foraminifera (PF) is known to have increased especially during the last 12 Myr, probably in terms of an adaptive response to an intensification of the surface-water stratification. On geologically short timescales, the test size in PF is related to environmental conditions. In an optimal species-specific environment, individuals exhibit a greater maximum and average test size, while the size decreases the more unfavourable the environment becomes. An interesting case was observed in the late Neogene and Quaternary size evolution of Globorotalia menardii, which seems to be too extreme to be only explained by changes in environmental conditions. In the western tropical Atlantic Ocean (WTAO) and the Caribbean Sea, the test size more than doubles from 2.6 to 1.95 and 1.7 Ma, respectively, following an almost uninterrupted and successive phase of test-size decrease from 4 Ma. Two hypotheses have been suggested to explain the sudden occurrence of a giant G. menardii form: it was triggered by either (1) a punctuated, regional evolutionary event or (2) the immigration of specimens from the Indian Ocean via the Agulhas leakage. Morphometric measurements of tests from sediment samples of the Ocean Drilling Program (ODP) Leg 108 Hole 667A in the eastern tropical Atlantic Ocean (ETAO) show that the giant type already appears 0.1 Myr earlier at this location than in the WTAO, which indicates that the extreme size increase in the early Pleistocene was a tropical-Atlantic-Ocean-wide event. A coinciding change in the predominant coiling direction likely suggests that a new morphotype occurred. If the giant size and the uniform change in the predominant coiling direction are an indicator for this new type, the form already occurred in the eastern tropical Pacific Ocean at the Pliocene–Pleistocene boundary at 2.58 Ma. This finding supports the Agulhas leakage hypothesis. However, the hypothesis of a regional, punctuated evolutionary event cannot be dismissed due to missing data from the Indian Ocean. This paper presents the Atlantic Meridional Overturning Circulation (AMOC) and thermocline hypothesis in the ETAO, which possibly can be extrapolated for explaining the test-size evolution of the whole tropical Atlantic Ocean and the Caribbean Sea for the time interval between 2 and 8 Ma. The test-size evolution shows a similar trend with indicators for changes in the AMOC strength. The mechanism behind this might be that changes in the AMOC strength have a major influence on the thermal stratification of the upper water column and hence the thermocline, which is known to be the habitat of G. menardii.

Moisture Sources for Precipitation Associated With Major Hurricanes During 2017 in the North Atlantic Basin

AbstractThe 2017 North Atlantic tropical cyclone season was among the most active in the last two decades, with 17 named storms, of which six reached the major hurricane (MH) intensity: Harvey, Irma, Jose, Lee, Maria, and Ophelia. In this study, the water vapor sources for precipitation for these six MHs were examined using a Lagrangian approach. The particle dispersion model, FLEXPART, was used to identify moisture sources. Overall, the North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico were identified as the main moisture sources, supplying ∼75%–85% of the atmospheric humidity gained by tropical cyclones, which resulted in precipitation associated with the MHs. However, the South Atlantic Ocean also contributed considerable humidity (∼14%–20%), and the remaining ∼1%–5% originated from the tropical eastern Pacific Ocean. The accumulated moisture uptake higher than the 90th percentile generally appeared within approximately 3° to 5° of the TC trajectory.

Where does the moisture for North Atlantic tropical cyclones come from?

Abstract In this study, we identified the origin of the moisture associated with the tropical cyclones (TCs) precipitation in the North Atlantic Ocean basin during their three well-differentiated life stages between 1980 and 2018. The HURDAT2 database was used to detect the location of 598 TCs during their genesis, maximum intensification peak, and dissipation phases. The global outputs of the Lagrangian FLEXPART model were then used to determine the moisture sources. Using a K-means cluster analysis technique, seven different regions were identified as the most common locations for the genesis and maximum intensity of the TC phases, while six regions were found for the dissipation points. Our results showed that the origin of moisture precipitating was not entirely local over the areas of TC occurrence. The North Atlantic Ocean to the north of the Inter Tropical Convergence Zone at 10°N (NATL) -especially from tropical latitudes, the Caribbean Sea and the Gulf of Mexico- provides most of the moisture for TCs (∼87%). The Atlantic Ocean basin southward the ITCZ (SATL) played a non-negligible role (∼11%), with its contribution being most pronounced during the TC genesis phase, while the eastern tropical Pacific Ocean made the smallest contribution (∼2%). The moisture supported by TCs varied depending on their category, being higher for hurricanes than for major hurricanes or tropical storms. Additionally, the approach permitted to estimate the mean residence time of the water vapour uptake that produce the precipitation during TC activity, which ranged between 2.6 and 2.9 days.

Eastward Shift of Interannual Climate Variability in the South Indian Ocean since 1950

Abstract The subtropical Indian Ocean dipole (SIOD) and Ningaloo Niño are the two dominant modes of interannual climate variability in the subtropical south Indian Ocean. Observations show that the SIOD has been weakening in the recent decades, while Ningaloo Niño has been strengthening. In this study, we investigate the causes for such changes by analyzing climate model experiments using the NCAR Community Earth System Model, version 1 (CESM1). Ensemble-mean results from CESM1 large-ensemble (CESM1-LE) show that the external forcing causes negligible changes in the amplitudes of the SIOD and Ningaloo Niño, suggesting a dominant role of internal climate variability. Meanwhile, results from CESM1 pacemaker experiments reveal that the observed changes in the two climate modes cannot be attributed to the effect of sea surface temperature anomalies (SSTA) in either the eastern tropical Pacific Ocean or tropical Indian Ocean. By further comparing different ensemble members from the CESM1-LE, we find that a warm pool dipole mode of decadal variability, with opposite SSTA in the southeast Indian Ocean and the western-central tropical Pacific Ocean plays an important role in driving the observed changes in the SIOD and Ningaloo Niño. These changes in the two climate modes have considerable impacts on precipitation and sea level variabilities in the south Indian Ocean region.

Gracilaria parva sp. nov. (Gracilariales, Rhodophyta) a Diminutive Species from the Tropical Eastern Pacific

DNA sequencing of the plastid encoded rbcL gene supported by morpho-anatomical features reveals Gracilaria parva sp. nov. from Panama and Ecuador in the tropical eastern Pacific Ocean. In the rbcL phylogram, G. parva occurs in a clade sister to the western Atlantic species G. galatensis. Morphologically and anatomically, G. parva is distinguished from two similar, described tropical eastern Pacific species, G. brevis and G. veleroae by its small size, to 2.5 cm tall with branch widths mostly &lt;2 mm occasionally to 4 mm, and by its two to three cell layered cortex. Gracilaria brevis and G. veleroae are taller, have wider branches, and a one cell layered cortex. DNA sequencing is needed to resolve the many diminutive species in the tropical eastern Pacific, particularly those occurring in turf communities. DNA sequencing of historical type specimens from the 19th and 20th centuries is also needed to correctly apply names in this region.