在Blazor应用程序中，将带有声明的JWT传递给Web API服务可以通过以下步骤实现：

1. 在Blazor应用程序的Startup.cs文件中，配置JWT认证服务：

public void ConfigureServices(IServiceCollection services)
{
    // ...

    services.AddAuthentication(options =>
    {
        options.DefaultScheme = JwtBearerDefaults.AuthenticationScheme;
        options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
    }).AddJwtBearer(options =>
    {
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidateAudience = true,
            ValidateLifetime = true,
            ValidateIssuerSigningKey = true,
            ValidIssuer = "your-issuer",
            ValidAudience = "your-audience",
            IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("your-secret-key"))
        };
    });

    // ...
}

2. 在Web API服务的Startup.cs文件中，配置JWT认证服务：

public void ConfigureServices(IServiceCollection services)
{
    // ...

    services.AddAuthentication(options =>
    {
        options.DefaultScheme = JwtBearerDefaults.AuthenticationScheme;
        options.DefaultChallengeScheme = JwtBearerDefaults.AuthenticationScheme;
    }).AddJwtBearer(options =>
    {
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidateAudience = true,
            ValidateLifetime = true,
            ValidateIssuerSigningKey = true,
            ValidIssuer = "your-issuer",
            ValidAudience = "your-audience",
            IssuerSigningKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes("your-secret-key"))
        };
    });

    // ...
}

3. 在Blazor应用程序中，使用HttpClient发送API请求时，设置Authorization头部为Bearer token：

@page "/fetchdata"
@using System.Net.Http
@inject HttpClient Http

Get Data

@code {
    private async Task GetData()
    {
        var token = "your-jwt-token";

        Http.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);

        var response = await Http.GetAsync("api/data");

        // 处理响应
    }
}

4. 在Web API服务中，使用[Authorize]特性来保护需要认证的API路由：

[ApiController]
[Route("api/[controller]")]
public class DataController : ControllerBase
{
    [HttpGet]
    [Authorize]
    public IActionResult GetData()
    {
        // 处理请求

        return Ok();
    }
}

请注意，上述代码示例中，需要将"your-issuer"，"your-audience"和"your-secret-key"替换为实际的值。此外，还需要根据实际情况进行适当的错误处理和异常处理。