Submarine Groundwater Discharge Differentially Modifies Photosynthesis, Growth, and Morphology for Two Contrasting Species of Gracilaria (Rhodophyta)

Round 1

Reviewer 1 Report

This paper is well constructed and supplies important knowledge about the relationship between fresh SGD and marine biota to the reader of Hydrology. I don't have any major comments on this manuscript. I listed several minor comments.

Introduction: The authors should describe that this paper focuses on fresh SGD impacts on marine biota because SGD usually includes recirculated seawater.

L123-124: I can't understand ETRmax, alpha, and Ex. Please describe these words.

L128: What is MASL?

L157: 1300? 13:00? Please check through the manuscript.

L253: Change from N+N to NO₃-+NO₂-. Why did you consider NO₃- and NO₂- as a nitrogenous source? Don't you need to include NH₄+? Several samples include ample concentrations as N source (> 1 µM, Table A2). 

L472-474: Generally, nitrogen uptake process occurs isotope fractionation. Therefore, δ15N values of product (G. salicornia and G. coronopifolia) and substrate (NO₃-) do not necessarily show similar value. 

Author Response

Please see the attached word document for authors responses. Thank you. 

Author Response File: Author Response.docx

Reviewer 2 Report

Review of: “Submarine groundwater discharge differentially modifies photosynthesis, growth,
and morphology for two species of Gracilaria (Rhodophyta)” for the Journal Hydrology
authored by Daniel W. Amato, Celia M. Smith, and Thomas K. Duarte
Overview: This paper presents summary of field and laboratory experiments to understand the
effects of submarine groundwater discharge on the distribution, abundance, and
growth/productivity on 2 species of Gracilaria. There was compelling evidence that there are
large impacts of SGD on the spatial occurrence patterns of Gracilaria.
Specific:
• Line 58: In this paragraph I was hoping to read something about where the invasive
Gracilaria salicornia came from. I did not see anything subsequently in the manuscript
so it would be good to know more about the biology of the species here.
• Line 72: The last 2 sentences are stating results, they have no business being in the
Introduction unless this is a journalistic preference I am unaware of.
• Line 89: Clarify how the 3 locations here and shown on Figure 1 span a gradient of SGD?
Okay this is elaborated on starting at line 128. But add at line 89 that SGD gradient
discussion is forthcoming, or don’t mention at all until later.
• Line 155: Useful to tell reader where the tide station #1612340 is located.
• Line 184: The statistical analysis does not benefit from a wealth of modern approaches
available. The traditional tried-and-true approaches can be fine, but this sends me a
quick warning flag that none of the authors are truly quantitative. If I used Sigmaplot for
statistics I don’t think I would admit that, just saying…
• Line 238: For the multitude of pairwise comparisons done was there a commensurate
adjustment to the degrees of freedom, like a Bonferroni adjustment?
• Line 257: The synchrony of measurements with water height is compelling and raises
questions about the vertical stratification, or lack thereof, of the water column. I hope
this is discussed further in the paper. Not seeing that, it should be discussed. Are the
nutrients distributed uniformly? Certainly, there is substantial vertical salinity structure.
Does the probe for the data loggers reside at the same location above substrate for all
trials? Was it near the substrate or well above it? I am not familiar with a CTD-Diver, is
this implying a person was in the water with a handheld device taking measurements?
This also refers back to Line 146 or so, but were the water samples taken at the surface
of the water or throughout the water column?
• Line 319: I have a hard time with deciphering Table 2. I am not sure how to make this
easier to follow when I still don’t fully understand it. There is so much information here
it may be better to somehow split things off, but again I have no clear advice other than
to say this table is not working for this reader/reviewer. Likewise Table 3.
Summary: I think there is compelling science here that warrants publication. I have slight
concerns about the statistics and all the pairwise comparisons performed, and the complexity
of the 2 tables.

Author Response

Please see attached word document for authors responses. Thank you. 

Author Response File: Author Response.docx