Describe What We Did For Both The Neuston And IKMT Tows

describe What We Did For Both The Neuston And Ikmt Towslife At Th

During our field trip, we employed various marine sampling techniques to investigate the composition and distribution of marine organisms at different depths and times. Our primary tools included the use of neuston nets and the Isaac Kidd Midwater Trawl (IKMT) to collect samples from various water layers, providing insights into the biodiversity present at distinct oceanic zones and conditions. The objective was to preserve the integrity of different biological samples across day and night, and at different depths, to better understand their ecological roles and life cycles in situ.

We began with neuston net sampling during daylight hours, deploying a smaller net from the side of the vessel to collect surface-dwelling organisms. Neuston organisms, such as calanoid copepods, comb jellies, and larval fish like the Pacific Sanddab, which exhibit lateral eye movement, were captured. These organisms are primarily affected by surface water exchanges and are crucial to understanding surface ecosystem dynamics. The small neuston net’s design allowed us to collect an array of planktonic and nektonic species that inhabit the air-water interface.

Subsequently, we conducted multiple IKMT (Isaac Kidd Midwater Trawl) samples at different depths and times. During the day, at 100 meters depth, we deployed the IKMT to target midwater organisms adapted to that light regime and pressure. The trawl’s design, with a cone-shaped net and a depressor, enabled us to effectively capture fast-swimming pelagic species including pyrosomids, heteropods (sea butterflies), salps (like Phronima inside a salp), and bioluminescent organisms. We successfully collected diverse gelatinous zooplankton, crustaceans, and nektonic fish such as lantern fish and midwater eel cods, which are part of the mesopelagic community inhabiting mid-level depths.

Nighttime IKMT sampling at 950 meters provided a contrasting view of the deep-dwelling benthopelagic community. Organisms such as large hydromedusas, red mysids, euphausiids, decapods, transparency-seeking sergestid shrimps, and benttooth bristlemouths were among the species captured. The collection of bioluminescent species like pyrosomids and elephant heteropods showcased the adaptive strategies employed by deep-sea organisms in low-light conditions.

Further, a subsequent night sample at 100 meters allowed us to compare diel variations in species presence and abundance. The organisms retrieved included myctophids, ctenophores, sergestid shrimps, arrow worms, and luminescent heteropods. These organisms play critical roles in the biological carbon pump and in the transfer of energy up the food chain among pelagic ecosystems. The use of bioluminescent observation, facilitated by a dark bucket experiment, provided real-time evidence of these organisms' survival strategies in darkness, confirming the importance of light as an ecological factor.

Throughout the sampling process, the combined use of neuston nets, IKMT, and visual observations allowed us to document a broad spectrum of marine life, from surface plankton to deep-midwater nekton. These methods, integrated with environmental measurements such as water temperature, salinity, and depth, contributed to a comprehensive understanding of the vertical distribution and functional roles of marine organisms under different conditions. The systematic approach, with replicate samples at various depths and times, emphasized the dynamic and stratified nature of marine ecosystems, revealing patterns of productivity, bioluminescence, and species diversity essential for ecological studies.

Paper For Above instruction

In our marine field studies, detailed sampling techniques were employed to investigate the diversity, distribution, and ecological roles of oceanic organisms at different depths and times of day. The primary tools included neuston nets for surface collection and the Isaac Kidd Midwater Trawl (IKMT) for capturing midwater to deep-sea organisms. These methods, combined with environmental measurements, provided a comprehensive overview of pelagic biodiversity and ecosystem dynamics.

Initial sampling involved deploying a smaller neuston net on the side of the vessel during daylight hours to collect surface-dwelling organisms. This surface net effectively captured calanoid copepods, transparent comb jellies, and larval fish such as the Pacific Sanddab, characterized by moving eyes to one side, which are indicative of their larval stage and adaptive morphology. Neuston organisms, living at the interface of water and air, are highly influenced by surface exchanges, including wind and wave movements, making their sampling critical for understanding surface habitat conditions.

Subsequently, midwater trawling was performed with the IKMT at different times and depths to encompass diel and bathymetric variations. The daytime IKMT at 100 meters captured a variety of gelatinous zooplankton such as sea butterflies (heteropods with wing-like fins), Phronima parasitizing inside salps with embryos visible inside its transparent body, and luminescent pyrosomids. These species are integral to midwater food webs, with many participating in bioluminescent interactions that serve as communication or predation strategies in the mesopelagic zone.

The longer-duration night trawl at 950 meters yielded a different assemblage, including large hydromedusae, red mysids, euphausiids, decapod shrimp, and sergestid shrimps with transparent bodies and red markings. The presence of benttooth bristlemouth and lanternfish illustrated the dominance of bioluminescent vertebrates and invertebrates in the deep-sea environment, highlighting their adaptations to perpetual darkness. Additionally, the collection of pelagic red crabs and jellyfish underscored the trophic complexity of deep pelagic ecosystems.

At night, another IKMT sampling at 100 meters allowed comparison with daylight organisms, revealing an increase in bioluminescence and shifts in community structure. Notable species included pyrosomids, myctophids, ctenophores, and arrow worms, many of which exhibit bioluminescent capabilities that facilitate prey attraction or predator evasion. Using a dark bucket collected in darkness, we observed bioluminescence directly, underscoring the ecological importance of light emission mechanisms among deep-sea species.

Throughout all sampling events, the observed organisms demonstrated stratified distributions and diel cycles that are characteristic of pelagic ecosystems. The surface community was rich in copepods and larval fish, with bioluminescent gelatinous species making up the midwater and deep communities. These biological patterns are driven by factors such as light availability, temperature, and pressure, affecting organism behavior and survival strategies. The collection data contributes valuable information to the understanding of pelagic ecosystem structure, energy flow, and adaptations in stratified oceanic layers.

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